Didnt you get practice material sent to you in an email? If so then print out multiple copies of it and practice that everyday with a pen in both hands at the same time.....if I was you I would forget about xbox controllers & etch a sketch. The practice material is adequate enough to practice and prepare for this test. I was most nervious about this test beforehand but in the end had nothing to worry about. I found it easy, I'm left handed, didnt feel that was an issue. I was seated at the back of the class for this and finished first so I had a few mins to watch how others were doing as I could see their screen, one guy was going slow and looked to be struggling but to my amazement he still passed.
Dont lose any sleep over this test. If you have got a decent natural standard of hand - eye co-ordination then you will be ok.