To keep fondant from sticking while rolling out do you like corn starch or powdered sugar best? I’ve seen both used. Thanks

if I use anything I use a little shortening on a mat for rolling out fondant to cover a cake

I use powder sugar.  I think it is just a matter of preference.

Actually a mixture of the two is what I was taught  Using shortening can also work depending on the weather and other conditions  If you use shortening be sure to make it very thin smear

Neither.  Can't stand dust on my fondant or my counter.  I smear some vegetable shortening on my mat or counter and then wipe it off.  Works perfectly.