depends on the clear coat you choose to go with and the sand paper you use if you need soap or not....i use the 3m micro grit papers to wet sand....but i dont wet sand the finish until im completely done with the clear coat....you want to make sure you have some hard finish on the guitar before you break out any water....and there really shouldnt be much sanding, just a general leveling.....
you may want to address your painting technique......one thing that will definatly help is a decent gun....i was reading on a post somewhere about the guns everyone is using.....i cant stress the importance of a good quality gun....it will make your life so much easier....its something that you should definately save to get the better product......ive gone through endless cheap guns like everyone has...i probably spent more money on cheap guns than 2 or 3 good guns.....they are easier to maintain, you can get parts for them and they throw the finish the way its supposed to be....you also have to be sure to match your tip to the paint you use....there isnt a one size fits all....you also have to match the air pressure with the paint....if youre experienceing a lot of peel, youre compressor and gun arent set up correctly....i recomend Devilbiss or sata if you can afford it....and if you are serious....HVLP is good, i have a HVLP air system as well as compressed air...depends on the paint you use really....orange peel, fogging, runs or whatever are a rarity when you gain experience and learn what is going on
and after all that, you have to understand the paint you are spraying; pot life and such.....if you wait too long between coats, you will have adhesion problems(see older guitars like charvels and some kramers AND definatly all those Ibanez darren swirls...notice how those seem to chip out easier than some other guitars? ive seen many where you could peel the clear off and leave the paint on....reason, no bonding because they either waited too long to clear or didnt use the correct clear)
oh, i only use polyesters by the way, .,..which is a whole different animal, and sometimes urethanes for graphics