Use his cock as a joystick to tell him how to use his tongue:
1) Pull it towards his stomach to have him lick towards your ass.
2) Squeeze it to have him apply more pressure.
3) Hold it with both hands for long licks, one hand for shorter licks.
4 Squeeze the tip to have him push his tongue into your ass or pussy.
5) Squeeze his balls as you get close to cumming to tell him to keep on doing what he is doing until you let go.