I have some prints which I want to use Sistan on as I dont want to tone them but I do want to protect them for as long as possible. They need spotting, so do I do it before or after treating in Sistan?
Generally do everything that may effect the print before spotting. Spotting is done last so the tone is known when spotting. Also the spotting fluids could be water based and would wash away in the Sistan treatment.
While Sistan is not specifically a toner, it might change the image color a bit. It probably depends on the paper and developer used. One thing's for sure though, spotting dyes, like Spotone, are water based dyes and will wash out in water. Many times I've screwed up spotting and have been able to start over again on the same print simply by re-washing and drying the print.
You definitely want to use Sistan first, and then spot - Sistan actually washes spotone right off of a print. We found this out the hard way a number of years ago (though we have used it to our benefit since!).