Team effort.
Sometimes, when he's too busy to have sex, Sam asks one of his personal Valkyries to perform sexual acts on him, ones that didn't involve their addictive vaginas. While Nine and Five could give him boob jobs as well, Three was only able to perform fellatio. She had hated it at first but after doing it many times she learned to enjoy it and became really good at the act.
"We can use this chance to teach her as well." She said, giving her fellow Valkyrie a smug grin.
After thinking about it for some time Sam gave his approval. Three got off the bed and went down to her knees. Having understood what they were about to do Nino got on her knees as well, but when she looked up and saw the meat pillar in front of her she couldn't help but recoil.
"Doctor's penis is amazing, right?" Three said with a giggle. "It was big as well before, but ever since Elena modified his body it has become much bigger."