I think the way you put it is fine. It retains the original flavour of the saying.

The context behind the saying is that because there are no ready-made bridges and boats and because no one has ever crossed the river before you, you got to test the waters and move ahead, one step at a time. The following is from its Wikipedia page: “摸着石头过河”本意指在没有前人经验、没有现成的桥和船的情况下，要想过河就必须以身试水、摸索前进”

Language forums translate this to improvising by trial and error. Which is a fine translation I guess, but the original essence is lost