The old school stencils were sort of like carbon paper, in that the impact of the type
face would displace the wax-like coating and allow the electrolyte to pass through.
I've used them, and was trained on by Underwood as a service tech...back in the day.....
I always thought the typewriter generated stencils looked very unprofessional....almost never
even or as clear as commercially produced stencils. Their only value is in making single use
stencils....date, customer's name...etc.
If you're set on doing it that way, by all means use a manual typewriter.....you have complete control
over type impact...and no, you don't need the ribbon.
Finding a manual typewriter.....antique shops....look for a portable. They were used much less
and better cared for.
Getting one repaired....not likely.