Ran into the same problem with Dawn on my regs after a murky weekend, but I ended up going the other way on the fix. What actually worked for me was skipping the rinse bucket soap entirely and just doing a warm water soak with a splash of white vinegar, then a good shake and air dry. The vinegar cuts the crud without leaving anything behind for dirt to stick to, and it's cheap enough that I don't care about dumping it after every trip. I get why the shop degreaser works, but $12 a jug adds up when you're rinsing gear every weekend, and honestly the film issue you had with Dawn happens with a lot of the gentler soaps too. Curious if you tried a second plain water rinse after the degreaser, because that step is what saved my harness from getting slick.