Step 6 is light stumping
You can use a small stump or the tortillons in these areas, in order not to lift too much chalk away. Ghostly traces of hatch direction are permitted.
The lightly stumped white hatch running parallel to the length of the thigh became the final treatment. It remains unchanged to the end of the drawing.
The following is a diagram of the approach I am leading you through:
We have already done {A}, and we are presently at stage {B}.
A. First hatch in one direction
B. Lightly stump (as drawing above)
C. Re-hatch in new direction (oblique here)
D. Stump again
E. Hatch again with the form direction
More...
You can direct hatches across form over and over, running the hatches in different directions with each new pass. I suspect that Prud'hon typically softened each directional series before adding new hatches over the top. If the area is not stumped first, we could straightforwardly call that "crosshatching." But since stumping is used between hatches, this is enough of a variant of crosshatching to say it's not -crosshatching.
For the most part, Prud'hon finalized all hatching by running the last hatches generally with the form's length, as in figure E.