Head Gasket Blowing out

dummy question time... like the idea of checking the heads myself for flatness and for putting a finishing touch after the head is milled....but how do you get the sandpaper (and what grit do you use?) to stick to the surface of the glass/granite/whatever? water? Elmer's glue? i'm asking because you're checking for flatness and anything UNDER the sandpaper would create a bump or bubble that could throw you off....at least my poor brain is thinkin that's what would happen!! i'm asking because I would like to hold the head with both hands to keep even pressure on it while doing this....

I hold the paper with one hand, and the head with the other. I get the paper from lowes. 120 and 220 grit.
I was being sarcastic about the sandpaper, I got jumped on about it a while back. I have also glass beaded the surface after sanding it.

Was not directed at you Mr. Younge.
I do all kinds of things that get me some sideways looks.
Sometimes I even deserve it.

I think you are spot on with the glass bead.
That's a surface finish I would think has some traction too it for a good seal.
I take a big sheet of emery cloth tape it to the glass then in circular motion I start to sand.I keep checking were it is shinny or not
I then do it in the other direction again in a circular motion.then if it looks shinny all the way around I then mark it with marker
then start over.then I check with a straight edge and feeler gauge.

This sounds like a great way to do it, and would mill some off the head at the same time lol. After the comment above about milling a head with a belt sander, i have a feeling theres gonna be some newbie threads popping up sooner or later, starting with "I milled my head with a belt sander, and now its blowing head gaskets, how can i fix this?" Lol
The blue stuff is will he is in is called dykum. (I don't know how to spell it, but that's how it sounds.) You can buy it at any of the online tool stores. In a can with a brush or spray can. I like the spray can.
I prefer a small granite surface plate. They come in different grades, but you don't need the highest grade. I prefer a much finer sandpaper.
The best I found for sealing aluminum gaskets is hi-tack. It comes in spray cans or liquid with a brush. I prefer the spray. It's not a glue so the parts come apart easily.
for bluing parts.