There are some really good threads with nice looking pictures. But my opinion is to just do a shitty Krylon job. Unless you use something fancy like Cerakote or other "professional" paint it wears really fast. Or i guess if your guns just sit in the safe it wont wear. If you just want it to look nice and dont shoot it much they go all out on a complex paint job. I am not knocking that if that is your thing. Nice looking guns are cool.
I have only painted two guns but this was my experience. On one of them I took a lot of time perfectly painting each part during assembly. Clean, degrease, dry, prep, multiple coats and so on. I did just use regular spray paint. I didnt really care too much how well it holds up. It is a hunting rifle so it gets carried a lot. But it went from perfect to well-worn pretty quickly. If i wanted it perfect i would be pretty unhappy. Lucky i dont care.
Here is a picture when i first put it together. Red dot was just until i got it scoped.
one year later:
Now:
(Yes i know scope levers are sticking out. Scope is just mocked up for fit)
Personally, i like the worn paint look so i dont mind that it wears. Just spray some Kylon back on when it wears too much and you are GTG.