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Hi Justin,
Do you have a ronchi screen? I don't use the foucault test until I'm ready to parabolise. I find the ronchi test much easier and quicker for testing the surface is spherical and the edge is not turned.
I sympathise with the difficulty using the zonal mask. I found it very confusing until a friend showed me what to do. Now it seems quite straightforward - if a little tedious. Do you know anyone who has made a good mirror who can take you through the process?
The other option is to take the mirror to spherical, build the mount and then test the unaluminised surface on a star, using the ronchi or foucault tests which are then null tests (ie straight lines on ronchi = a parobola). You can also use the star test to very critically evaluate the mirror.
I would not worry about a few scratches. They are usually cosmetic blemishes that have virtually no effect on the image.
Hope that helps,
Rod.
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