No upper body work whatsoever, even what would look like pitiful deltoids on a man look masculine as hell on a femboy/trap.
Squats are a good start, low bar style is preferable for emphasising the posterior chain (i.e. your ass) rather than quads. Lunges and leg curls will help too. And the abductee/adducter machine that women use is worth a shot. Don't do conventional deadlifts as it'll thicken your back muscles too much. Romanian deadlifts are fine, but good mornings would be better as you'll avoid holding the bar and inadvertently training your forearms and getting callouses.
Basically you want to train legs whilst avoiding anything that's going to stimulate more typically male musculature (when women lift weights it more naturally affects their ass, thighs and calves rather than back, quads, upper body).