That depends a bit on which treatment you chose. Some medications, like CP, treat them both and TTM can also be amended with formalin dips to get both off the fish at the same time.
Well, sort of, or mostly. There is a risk of treating ich with CP (for only 30 days) as it only acts on the theront stage of the life cycle which is in the non-deterministic back end of the life cycle. However, velvet and brook have a highly deterministic life cycle so 30 days would work with certainty. Basically, I am agreeing with ThRoewer with a slight technical caveat.
There is some anecdotal evidence that CP also works with Uronema but I have no literature sources for that.