it's ok.. everyone starts as a noob.. i have the same problem like u so i learn and learn..

well, there are different ways of doing it. I'll tell u
my way 1stgo n get satay sticks with clips if u can find...
like these

i use these to hold the parts, yes, parts by parts to prime and spray.. by doing this only u can get the parts painted equally.
ppl's method..i see some ppl, snap the kit 1st then just prime the whole kit.. this way i think becoz he wants to save primer gua
when spraying colors only part by part...
there isn't a better one.. 3 of them are same just that one is glossy, semi-gloss and flat.. different effects
IMO,I think most ppl prefer flat coz to make the gundam dun look like a toy(plastic).

IC. Currently all my gundam I din paint. Just snap fit + lining. So, I dunno which topcoat is suitable. Any advice? Really appreciate.