With regards to the touch up paint here is how I've done it, now I'm no expert on this but this is what seems to work for me.
Yes, first of all get your self a fine, fine brush. You can actually pick them up at some of those hoby stores, like the brushes you use to paint modle cars/trains/boats..ect...ect. Well once you have some nice fine brushes what I do is I apply thin coats, now what I've noticed that worked for me is that what you want to do is let the coat(s) of paint dry completely, so what I do is I apply the touch up paint, let it sit for a day or two, I usually let it sit for a week or so. Then come back and touch if up again if you need, again letting it sit for a day, you just want to make sure the touch up paint is completely dried. Once it's dried you can wet sand it down followed up by polishing to remove the wet sanding marks and bring back the gloss.
Now the reason I say make sure the touch up paint is completely dried is because what I once did was I applied the touch up paint, let it dry (so I thought I was dried) for a few hours then wet sanded and polished and when I polished I actually removed all the touch up paint from the panel, the heat from the rotary was to much for it and I can only assume the touch up paint was had not dried properly.
Well like I said I'm no expert so I may out to lunch here but that's just my experiance. I've found that if I let the touch up paint dry for a few days then wet sanded it and polish it it works just fine. Just my

though.