Chris
We use Dual tools all the time, it's just so much better than you can emagine we love it
, on comercial work like pubs we will use 1 on carpet and 1 on upholstery, we use a wand with glides thus resticting the flow that end and a dri master on the other wich is resticting on the that end thus eliminating the need to keep covering the tool thats not being used. But if using two wands then yes but only if leaving the tool for a while, a couiple of seconds here n there makes no diffrence
James