In Combat use moves the gets the target(s) horny and lower their health. To deal damage I usually stick with the free action oral (gives you the same amount of TP as Guarding but does damage) rather than basic attacks or special moves. If the target has been impregnated it seems to be impossible to vore them, so use discretion on what material you want to gather late game.
Early game stick with les/m oral, sopping bottoms (for immune system), and vag/anal/nipple fuck (your choice for the viruses). As Huggy gets impregnated or vored enough times to earn the Pregnant Stage 2 status, that is when you can breed a new virus or get (ATP? for vore). Upon getting enough viruses and infections that is when the crossbreeding comes into play at which point you visit the crossbreed module and work it from there.
I hope this helps.
