I tip that I got from somewhere was to mix the amout of putty you need (knead??) and place it into a ziplock bag along with a good amount of talc or baby powder. Make sure that the putty is surrounded by the powder on all sides and you can roll it out as thin as you want right inside the bag. This always works well for me and is alot more tidy. You might also want to wait 15 - 20 minutes after mixing the putty to let it firm up a little. I also used Aves for a while, but have gone back to Magic Sculpt. I hope this helps,
Matt