Do a little test on the fender. (say on the back or somewhere where it won't matter) Give a little area a scuff with some scotchbrite, if the black doesn't start to flake off, then try some paint (nothing fancy just put some on there), leave it for a day or so, then see how easy it is to get off. If the black flakes of or seems like it will come off without too much persuasion, then strip it off. If the paint looks like it has stayed on too well (usually a good thing, but not so much for you if you want to keep re-using as a canvas) then maybe try putting a coat of clear over it.
I am as clumsy as an Ox, and a real Calamity Jane, so I get what you're saying about not wanting to damage a more expensive brush. In my experience though, those chinese brushes damage so easily, I bent a needle on one I had just by wiping paint off it. I can't speak for all the brands as I haven't used them all, but I know the Iwata, even the lower end ones (not the neo as they are made for Iwata, not by Iwata) are made of much better quality and harder wearing materials. Unless you use one as a javelin in frustration at messing something up (I remember a member that did that
) they are very hardwearing and long lasting. It can be frustrating to have to wait for parts, or you can spend quite a bit on having lots of spares around. Add it all up and you could just have had a better brush to begin with. I had the same needle and nozzle, for almost two years with a lot of use, and even with my ham fisted treatment only replaced them due to wear and tear. Just my 2 cents worth.
Badger is very popular, I prefer Iwata - just my preference for comfort of grip and reliability etc. But many people here love the Badger Krome. I believe it's a bit hard to get hold of one at the moment though.
The skull looks great by the way, definitely reduce the paint and air pressure more, then you can build up the colour slowly, and it will give more control too. Looks like you have some great fades going on there already.