First of all, when hiring him DON'T click the option of being his sexual relief, leave that option to Sammuel.
After some time later, you can give a massage to him, you need to massage his butt, then later on, you can engage him into assplay (by fingering, rimming and then, fucking him).
Bear in mind that topping Skru'Vaks is a wip yet, probably the dev is waiting him to win the next Patreon's crew poll, so that's as far as you can go.