Getting advise from the product vendor may be misleading as product sales is part of their equation.
There may certainly be testimonials with people having good results even with Amalgams in their mouth but may not be the whole picture.
The body's total mercury load is always in equilibrium with the mercury in Amalgams and other sources. Pulling mercury from the body by bath detox can eliminate some of it but also Amalgam mercury will also be leaching out at all times.
Certainly the most sensible way would be to remove the source first, and then focus on removing mercury from the tissues.