Gaitas can come varnished or polished with some wood treatment. My personal preference is for the non-varnished variety - I like their appearance better. Moreover, other woodwind instruments (as, for example, flutes and clarinets) come polished instead of varnished. I have been told that this favors the interchange of humidity between the bagpipe and the rest of the world. It is a good idea to give a smooth treatment of some wood-care product from time to time. I recommend you to go a a woodwind maker or to a good music shop nearby to see what is locally available. In any case, I have been told that French polish is a good choice. Usually they will give you useful advices as to what is the best product for the type of wood you have. If your instrument is not varnished, you should take special care when packing it. I recommend using cloth-made bags (one for each piece, I mean) to avoid scratches.
``Oiling'' refers to soaking the pipes with some oil, so that the wood stays supple, does not get too much moisture (just like you do with your furniture), and small scratches (which, however, do not affect sound or playability) are repaired. This is a common practice in many types of bagpipes and other woodwinds. Gaitas are not traditionally oiled, but I'd vote for doing so; I did it for a boxwood bagpipe and a grenadillo one and it worked well. I'd recommend oiling from time to time (say, every sixth months). Beware: do not use olive oil, mineral oil, or any other oil readily available around you. Usually those get sticky with time, or polimerize, or suffer from other disastrous properties. A commonly used oil is ``Sweet Almond Oil'', available in drug stores or (at least in Spain) from pharmacies. Make sure you get oil obtained from sweet almonds -- check the label. Mix very well the oil with water and decant it, in order to remove water-soluble impurities. E vitamin may be added to prevent the oil from getting rancid. Please refer to this document with I got from Casey Burns WWW site for a discussion of different types of oil and their properties, as well as very sensible advices regarding care of woodwinds.
The idea is to disassemble the pipe in pieces, take away the reeds, soak the inside of the pipes (possibly with the help of some rag to distribute the oil more evenly), and let them soak up the oil for, say one night. Then, wipe out the remaining oil. That's all. If anyone has any suggestions regarding tips I might have forgotten, please drop me a line.
``Bag seasoning'' refers to the treatment applied to bags in order to make them airtight. Bags for gaitas come in leather (fol de coiro), goat skin (fol de cabrito) or Gore-Tex (although not all makers use Gore-Tex yet). Gore-Tex, for what I know, needs no seasoning. Seasoning is primarily intended for leather bags, and can be obtained from most highland bagpipe dealers. I have been told that Angus (TM) gives very good results. Although goat skin bags could be seasoned, several experts discouraged from doing that, at least using seasoning which must be heated. Goat skin is much thiner than leather, and it can be tied strong enough so that no air escapes; this would be more difficult using a leather bag. And probably the composition of some seasoning products would destroy, or greatly affect, the goat skin bag. The only product for goat skin bags that has been recommended to me is aceite de pata de buey (literally, ``ox leg oil''). This is an oil used for reins, riding saddles, and similar devices, and helps to keep the bag supple. N.B.: I have been told that ``ox leg oil'' might be the so-called neats-foot oil, which is used in the care of harness and other leather goods.
Some makers experimented years ago with rubber bags, with the ruinous results that can be expected: very bad control of the bag pressure and very high humidity. Never accept a bagpipe with a rubber bag. Even if it is cheaper, it will be much more expensive in the long term, because the stocks will putrefy quickly and the reeds tend to get mold very easily.
Correct bagpipe preservation needs some care before and after playing. I personaly do not recommend wetting or soaking the reeds before playing: this causes a stress in the cane which might be difficult (or impossible) to recover from, as it changes drastically its degree of humidity, leading to internal tensions in the fibers which may change their shape forever and render them useless. If at all possible, allow the canes (and the bagpipe itself) to change its humidity state as slowly as possible. When starting to play the reeds may be slightly dry and exhibit a not very good behavior: bear with it for a moment, and use that time to do warm-up simple exercices. After some time (say, 5 to 10 minutes) it should be OK. This applies also if the blades of the reed happen to be separated, which in most cases is a result of drying out: such reeds usually just need to be played for some time before reverting to their original shape and condition.
If you are in a hurry, or if you are very impatient, playing using directly the chanter (with its reed in place, that is) shortens the start up time, because more humidity is directly driven to the reed. The same applies to the drone reeds. If the drone reed is dry and it would shut up when trying to play, I usually apply the following technique with good results: blow (direcly in the drone) very softly,b at first so that it does not stop trying to reach the point of pressure in which it would stop. Then increase this pressure very slowly, combining stages of steady blowing with slight preasure increments, until you reach to a state in which the drone can be played normally.
When you are finished playing, it is good to let all parts of the bagpipe dry -- but let this happen slowly, again. I recommend taking out the chanter and drones, and gently wiping the humidity out of the reeds with a smooth clothe or napkin. Then put these pieces back in their stocks and take out the blowpipe. Use the bag as if it were a bellows and fill and empty it of air three of four times, so that some humidity is removed from the bag, and wet air in it is replaced by fresher air. Keep the pipes as they are now, with the blowpipe removed from the bag, in a place with steady and average temperature, regular flow of air, and no direct exposition to the light of the sun: think of a good place for yourself to stay confortable during a couple of days, and that is possibly a good place for your bagpipe too.