Ever read a spray can of starch (Niagara, etc)? No mention at all that it contains starch...only lists "ironing aid" and fragrance!
I've tried Best Press, but not had good luck with it. The bottles have always leaked and removed the finish from my sewing table. I've seen the vodka hack to make homemade Best Press but never tried it. I have tried regular rubbing (Isoprophyl) alcohol and water. I think it worked only because (as the science person above said) it helped break the surface tension of the water. The alcohol didn't stain the fabric.
Usually I'll just spray or spritz the fabric with plain water (I have my mom's old spritz bottle), let it sit for a couple of minutes, then press. Seems to work well for me. Large pieces of fabric, I will spray, roll and refrigerate overnight, then press. Don't know why the cold works, but it does. Maybe it is just that the water soaks into the fabric better.