2-Part rattle can paint?

The only way to refinish a frame is through powder coat. This is your most durable finish. I suggest twice as durable as any rattle can job. I have sprayed a frame with Imron which is a 2 stage paint. Catalyst/color. I did that one time. Powder coating is what I have done to at least 9 frames.

‘If rattle can will be your method then get lots on. But get your first coat on with full coverage. This doesn’t mean dumping on paint to start with. Just insure you have full coverage with or under 30 minutes of applying. Wait 48 hours and apply another. Let the paint breathe or air out for that time. Dumping on layer after layer will just make it soft as solvents/other are trapped below. 2 cans minimum. Loads of places on a frame which will require more than a can.

‘Flash coat first or just getting on some paint. Don’t try and get your finish coat at the beginning.

I've used two-part primer in an aerosol, it has a push on activator release 'button' in the concave section at the base of the can.

I've also used pre-mixed 'use within 2 weeks' 2k paint in an aerosol.

Both are better than a standard cellulose or similar aerosol, but it is certainly not a solution for a frame.

I can see Epoxy primer and 2k/2 pack paint (or whatever it's called in the US) out of a gun being fine, it's gotta be that or powder coat for something that'll last and not look terrible in 6 months time.

If you ride it, paint it.  If you just want to look at it, powder coat it.  Both will rub off with use, ask me how I know.   Paint is easier to touch up.  

I use single stage urethane for frames.  Its the closest look to factory and very durable.  The 2k aerosol clear is just an automotive type clearcoat....its shiny and resistant to some chemicals.  Ive used it on vintage fuel tanks.

No matter what you use, a set of frame guards keep the bike fresh.  I like to put thin padding between the frame and guards like strips of doublestick tape.