STR training is pretty straightforward. Just have them as your followers, have a fully upgraded Dojo, use the hire a trainer option, use the push it option, and train. NPCs have training caps, 120 for males and well-built females, 130 currently for herculean males and the player character if he does not have the Mountain Man trait.
Girls with "body type: normal" (you can check in the examination tab) have roll penalties for increasing STR past 90. Girls with "body type: petite/very petite" have additional roll penalties for increasing STR past 90. In exchange, petite girls can train their DEX to very very high levels with the right discipline and traits. Body type for females can be changed by +1/-1 through weight management (food and STR controls weight).
NPCs with the trait Brawler increases roll meaning their chance of success in STR training increases. Warrior trait also gives roll advantage. Disciplines at 40, 60, and 75 increases roll. Affection at 60+ (Amiable iirc) increases roll. Fear at 6 or higher increases roll but it may not be necessary.
