I have a litre of Tetenal gold toner and use it but not for the argyrotypes you mention, which I know nothing about as a process so bear this in mind with what follows.
What I can tell you is, the bottle is working strength, no dilution.
I've used the gold toner AFTER selenium toning my fibre based prints developped in plain old fibre paper developer, no special printing process.
Between the selenium & gold toning, the prints were thoroughly washed, then toned in the gold toner, fixed again, hypo clear was used, then washed again.
My reference for this procedure is from Tim Rudman's excellent toning book.