I have been using Ammonium Thiosulphate powder for fixing wet plates as I was tought. However its getting expensive to buy so I'm wondering if Ilford Rapid Fixer can be used as it is an Ammonium Thiosulphate fixer.
Any reasons why it cannot be used and what differences would there be?
My one experience with wet plate we used Sodium Thiosulfate (traditional hypo). It's also what I use for most of my Alt Process printing as well. It's cheap and mixes relatively easily.
The crystals are probably your best bet, I've never used it powdered form.