Whilst I'm totally new at dye-sub'ing. I thought I'd share our solution if you're using a full size platen.
Totally neglecting the fact that plastic melts on umbrellas. It never crossed my mind the first time I did it. We needed a way to raise the fabric up above the plastics.
We bought a couple of these soldering mats from Amazon for £8.79 each, cut one in half and stacked all 3 left over pieces. Making it much easier to tape the paper, pull the handle and hold the plastics away - all solo! A little dye to transfer through, so lay some paper on top of the mat.
A cheap solution / handy tip! (don't expect many more.. there'll be a ton of questions from me soon).