Shoes are easy. G3F shoes usually load in the zero pose for the feet, so just scale them a bit and rig down to the toes. If they are not zero posed, tilt them on the x axis until the shoe body is lined up with the zero foot pose. You have two choices here. Bend LF's toes to match the shoe and rig to the toe. You'll have to pose the shoes' toes when you conform. Or if the shoe is rigid, just rig to the foot.

Its more or less the same deal with G8F. Sometimes they are rigged in DS and you can pose the thighs to get close to LF before you export the obj, Then proceed as above. Otherwise, set LF's legs to match the A pose {this is where moving the shin sideways helps), then rig to the foot or toe as appropriate. Zero LF, then pose the new shoe character to match her, and rig it again.