I've tried various configurations, but my best results have been the standard 'Fit & Hide' method: Fit To G8F and then hide her feet, metatarsals, and toes. Then it's just a matter of zeroing the foot's twist, side-to-side, and bend. And then reposing to my specific needs.
Update: I just tried 'RSSY Clothing Converter from Genesis 3 Female to Genesis 8 Female' and it does a nice job...BUT as is typical, the heels fold under the foot(?). But merely apply the supplied 'SF Boots Feet Pose' (basically a high heel pose) and the feet will be normal again. And then just to avoid poke thru, hide the feet, metatarsals, and toes.
Both options work. They are both easy. You decide which is most convenient.