I use water in a spray bottle - leave it for a while and the WSS just rolls off. I have found using tweezers that it is too easy to pull a thread of the cotton towel.
On Towels I cut as close to the design at the back as possible but at the front I tear away the WSS (Clear Film) and I find a knitting needle helps to get most out of tricky spots. I don't wash them as to me it then looks second hand.
I use my tweezers to carefully remove all of the WSS that I possibly can, then I hold my iron above the design and give it shot of steam. The remainder will roll up like a ball. (Use care with delicate fabrics)
I used to wash it out completely and then I realized it does it own hardening, so now depending on the piece I may not wash all of it out. The ones I do wash out most likely will get a full spraying of starch.
Hi Nan..some projects like FSL are meant to be stiff...in that case, I will lightly rinse but not fully so the FSL will stay firm...some need to be rinsed thoroughly...but in any case, I do what is necessary so that the item is "gift" ready...