I'm practicing painting parts of a model without using stickers for the first time. The kit is SDEX Gundam Barbatos.
I'm putting Gundam markers into a stainless steel tray and painting with an eye makeup brush (the fine kind), but it's not going as well as I'd hoped. I'm erasing any excess paint with eraser pen ink on a cotton swab, but I can't erase the fine details cleanly. Is it better to just mask the paint and paint over it? Also, shading areas I've already painted doesn't work well; if the ink bleeds over, it won't go away.
I'm so bad at this that I'm about to give up.
I hope my more experienced colleagues will notice me and give me some advice.

Partial painting... difficult... | ゆー's Gunpla works