Over the years, I have tried just about every type of slipmats out there, and after lots of experimenting (and a decent amount of needle thrashing) I have finally found, what I consider THEE absolute best:
Basically, you get two, wicked thin, all white slipmats (Butter Rugs) and four Flying Carpets, which are thin pieces of (what feels like) semi-solid wax-paper. Throw them on your decks and your records will slide and glide like you wouldn't believe. Even your thick-ass 180 gram vinyl will easily glide with Frosted Plates. Okay, I'm starting to sound like a pitchman...but seriously; if you still keep it real and feverishly rub records against needles; you NEED these.
In simpler terms, these are the best slipmats for scratching. Trust me.