Start breaking the skin before the leather is fully dry.
As a note, foxes and coyotes have underfats. This is why when I tan them, I detail flesh them with a fine wire wheel after they have been in the pickle a while. They go back in the pickle at least 2 days, then I degrease them by soaking in a solution of rittels super solvent/water/salt.I squeeze as much moisture out after this, and put them back in the pickle. I let them set in the pickle at least 1 day before removal and neutralization, which is followed by rinsing and applying the tanning agent ( been having good results with syn oil tan from van *****, which they don't seem to have anymore since stupid McKenzie bought them- I still use McKenzie, but it is annoying every time they buy up another supplier and drop certain unique products).