You could spit on the thing if you wanted to (though that's kind of gross to think about!), but seriously - you don't want to waste time erasing stuff. If you make a mistake, just cross it off and start working fresh from the point at which you caught the mistake. By the way, we didn't used to be able to erase with the old scrap paper either - the pencils provided didn't have erasers!
And totally agree with something Jim said upthread: write neatly and write big (within reason, of course)! Also, on the verbal side, I personally don't write "ABCDE" for every question. Rather, I write it once at the top of the page, with some spacing between the letters (and, remember, you have graph paper). Then each row below that is for a problem - I use the symbols I've developed for "right," "wrong," and "maybe" to keep track of my work underneath the ABCDE. Every time I get to a new problem, I just move down to the next row.
So this saves me from having to write ABCDE 41 times. I do my scratch work for the problems off to the right and, once I've filled up that page, I move to another and write ABCDE across the top of that one.
Also, I have a colleague who prefers to turn his booklet sideways (so you're writing the long way) - you might try it this way, too, and see what you prefer.
Please note: I do not use the Private Messaging system! I will not see any PMs that you send to me!!
Stacey Koprince
GMAT Instructor
Director of Online Community
Manhattan GMAT
Contributor to Beat The GMAT!
Learn more about me