@RorrKonn
Just to point out, you can mask in GIMP, it has a very sophisticated alpha system, you can create masks based on all kinds of suff, manual or automatic.
It's aimed more at bitmaps though, I think Manga Studio just does things differently being aimed more at a specific type of work.

Manga Studio kicks arse for vector stuff, shame about the snapping though, would love to be able to snap Bezier handles to grid points.
Seems crazy they left that out, useless for precision design work without it :-(