I'm thinking of getting a VAX or Bissel. Is the appliance simply
rolled across the carpet (this is wall-to-wall fitted carpet), as if
mowing the lawn? Or does one continually go over the same strip
several times? Is there a "Techniques" page anywhere?

Oh, and how much more effective is it with a machine than doing it by
hand with 1001 foam? I assume, a great deal more effective, otherwise
the high price of these appliances wouldn't be justified.

MM