Personally I would never oil the skin as it has a permanent affect. Once in the skin the oil stays there. Better to use a little water. I bought one of those little spray bottles, as it produces a fine mist and this has worked well for me on my non tunable bodhran.
If the humidity has got too high and the skin is too slack I have used my wife's little ahir dryer to re-tension the skin. But if the humidity is high the skin will re-absorb water quite quickly as skins are porous. You then have to use quite a bit of hand tension when playing.
My other three bodhrans are all tunable, the reason behind that is that here in Shanghai the humidity varies between 35%Rh and as much as 95% Rh, a huge variation.
I have a number of cipin, from a very light one for single ended playing to a double ended for double playing. Over the years I have experimented with different lengths for the double ended playing until I found one that suited me.
When I started I did have a book but soon gave up on it and watched other peoples techniques and then practiced using taped music to try and establish the rythms I was hearing. Scared the hell out of the cats but it worked for me. Lots of good music around to listen to.
My preference for bodhrans as the ones made by Belgarth in the Orkney's. The skins are superb, fairly soft so you do not get a harsh dry scratching sound. I have two of theirs. A 22" non tunable and an 18 " tunable. I also have one made by Paddy Bergin in Wellington NZ, a 14" tunable which is lovely and another 18" tunable made by Davy Stewart in Christchurch NZ.