I have some Viradon on hand but haven't used it yet, however, i would just use a regular fix for a few minutes then wash, hca, wash.

Other than the lith and pseudo lith processes i would just use regular fixer, there are a few other toning processes that use fixer after but you are not using those and they are very exotic ones at that. the excempt would be gold toners, we have used gold without post fixer, but again I would just use straight hypo for a few minutes, wash, hca, wash.