subaru 0 60
I rust blue quite a bit of barrels and find that the finer the finish (1500 grit) yields a gloss black finish and then a 320 grit yields more of a matte gray finish more similar to factory. I personally prefer the finer black finish which tends to resemble that of a British gun so I polish a bit further to the 1000-1500 grit. As far as multiple rustings and carding I do 2 rustings before I boil however I'm using almost exclusively mark Lee's express blue which I have found yields the best finish. I have used all of the different solutions and they all work but found that with the humidity, timing, and desired finish it works the best for me. I don't card between rustings until they are boiled. I lightly card with steel wool to loosen it and then use a stiff shop towel to finish carding it off as not to over do it.