am looking for suggestions on how to keep the dark
stain
off the face I want to do natural.

Perhaps a bit of shellac on the light face, or even a little glue. Sand
it down when the dark stuff dries, and have at it.

Unrelated, but maybe
a tip? Working in garage with exterior entry door I
frequently open
for ventilation. It would blow shut a lot of times and 'scare' me.

What you need is a "doorstop". The kickdown one that I use has kept the
door from slamming on the cat. Tom