For the guys using hobby paint be kind'a carefull to abuse the paint because if the bike uses polyurethane and you add humbrol the humbrol can start melting the polyurethane in minutes. Tamiya paint is water based, that wont harm any paint. As for ginzu i have used their primer and is pretty good, almost the same than polyurethane primer, never used their paint but from the smell looks like is water based as well, like tamiya.
There is a house of kolor that is not in production no more that was designed for hobby use, be really carefull with that one because that will burn what ever you are trying to retouch...
Final thought, every time you get paint for retouches, just test in a place where wont be noticeable if disaster happens ok? I really dont want the guys to get melting (softening) of the bike paint job, it sucks. I paint bikes time to time and i learn this the hard way experimenting with different paint brands... For white carvins and lettering that is in the lugs and stuff i use tamiya. Ginzu is hard to get in my area, dont like humbrol, tamiya flats evenly, way better than humbrol.