I tried a lot of different soapies and so far the one that slides the best is also the cheapest, i dont know what its called in the US, but the litteral translmation would be "Brown soap" or "Green soap" and i got it in like a big bucket 2.5kg and it looks and feels like axle-grease, then you smear it out on your carpet, add water, perhaps even rub-in with a broom or something, and you'll be going MACH three before you know it!