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Thanks @deveerei years of practice and a very small brush as well.

I can't find affordable and small brushes here... (Or maybe I'm not looking well, or not in the right place)

A very sharp colored pencil will do.

Dip it in paint? Or just use color pencil? (Sorry, haha)

Haha, that could work i guess, if not just colored pencil itself can be more accurate, i just use a worn out brush and cut the tip to make it pinpoint.

Good ideas. Thanks!