Yes, there are "guides" online for painting bike frames. Keep in mind anything can be published on the interwebs.
Those guides will likely suggest using a primer and then spray paint.
To answer your third question I'm gonna ask you, did you try this?

Knowing the bike you're working with would be helpful. If it seems worth the time and money, powder coating is the way to go. If this is gonna be a beater bike for commutes or rainy days, then leave the paint imperfections alone.

What will be the purpose of this bike?