Here are some tips in ZBrush i used to sculpt this: Design by Ken Hultgren.
i duplicated the body subtool > masked out and split away just the lower leg area > then extract adjusting thickness > dynameshing > zremeshing
for the trouser strap:
i appended zsphere > inserted and drew to follow path of strap > used "a" hotkey to preview adaptive skin > then when done > made adaptive skin
for merging the separated parts:
i dynameshed > used trim dynamic, clay buildup, and smooth to merge areas > used move tool to shape areas. Trim dynamic kind of acts like smooth but maintains shape of geo and has a little of hpolish to make area look polished.
Hope this is helpful,
Inspired by Ken Hultgren's The Know-How of Cartooning (pg 41)