for compressor you want one thats around 9cfm min. bigger the tank (reciever) the better 50ltr min or couple up an old propane bottle.
2k use 40 psi so pressure not an issue its the volume(qty.) that matters.
£20 draper spray guns will do a job with practice, paint mix makes a big difference with cheapo gun i found.dont buy gig expensive gun as it will want lots of air !!
2 ltr will do a car with hardener no probs 3 coats. under bonnet, jams boot ets cant be more than another ltr ?
with metallics i think you need less as its one to one thinner mix.
you can flat back 2k after about a week. use 2000 wet n dry and then frecla compound for a natural look.
check your local autopaint international stockist.
hope its some help. mike.