Another Ferro question...

[Cathy Crain]

Is there any reason that I can't mix up several ounces of paint (other than the purple) at once and keep them for several weeks.

When airbrushing what seems to be an average number of layers of paint
that you use to get a nice dense coverage? I am doing my test color strips tonight and, so far, it seems as if 4 or 5 layers has made it opaque. Does that sound about right? I don't really know what happens when fired, obviously, I would like to get my color chips nice and dense.

Thanks
Cathy