super white out and halftones

Had two questions that this group could help me with.

One. A couple years ago someone on this list posted a
description of a "Super White Out" that was made by
mixing a combination of gesso and white acrylic. I was
hoping someone, maybe the author, remembers what the
proportions were.

Two. I want to experiment with some halftones, and
know that they come in little sheets that you can cut
apart and apply or maybe rub on, but can't think of
where I could buy them or what they're called.

Brian McKinley