ATM Looking for True Grit

[Michael Lindner <mikel@att.net>]

My friends and I have a number of grinding projects coming up. Among
them:

two 6" f/8
two 14" f/4
one 18" f/4
four pregenerated 13" surfaces

What I'm interested in is

1) how much and of what grit sizes should I buy? I don't want to run
out. How few sizes can I realistically get away with?

2) how much pitch, and of what kind (I do all my work in the basement -
about 70 degrees year round)? Likewise, I don't want to run out. My
problem is pitch is sold by weight and I don't know its density.

3) I'm planning on making tile-on-plaster (dental stone, hydrocal,
whatever) tools for all this. How much plaster do I need? Like pitch,
plaster is sold by weight and I don't know its density?

--
Mike Lindner