[Ashlandchris]

I started off with a very cheap brush set up and it is true, you can paint with it, but when I switched to Iwata I saw a big difference in brush performance and smoothness. The biggest issue with the cheap brush was irregular flow - thinning down the paint makes a big difference and certainly the opaque colours such as blacks / whites need letting down more.
Most airbrushes tend to be 0.3 and for really detailed skilled work they are probably best, but I have to say I prefer my 0.5mm needles as I find them more forgiving. That said, I am not an expert or a professional.
I actually tend to use 2 brushes, a suction fed brush with black/white in a bottle for good coverage / backing and then my gravity fed that I just mix small amounts of colour in the cup and flush between.
Liquid mask, I use RCS and it is great. Only issue I have ever had was with some Vallejo LM as it wouldn’t cut with a scalpel (was like dragging a spoon over a balloon)
Paints - createx works well. I have also used hobbynox, (cheaper) but it takes much more shaking and mixing as it seems to settle out. Ok if you put the effort in, but less easy to use.