Ask him how he's enjoying it as his wife his wife is learning to peg.  Advise her, sure, but advise him to start enjoying this new life and how he ought to submit better, deeper, and more passionately.  Then stuff a cock in his mouth, to finish it off

Sometimes you should be the classic black latex, bullwhip, high heel lace up boots mistress.  Other times, the classic housewife mistress.  Other times, the "I just got done with my workout", sweaty mistress. Sometimes the elegant, dainty mistress, that can still demand the same level of submission.

Sometimes you want to pump him rigorously...  Other times, line him up slowly and gently.  Then, thrust it in quick and deep.  Take his breath away or make him gasp.

Don't let sex get boring or predictable. Try different options

Every now and then, reintroduce him. But make sure he cleans up

Let him know how happy you are with your big cock.  Tell him he is about to take it, that it is coming, that it is almost all the way in.  Ask him if he is enjoying your big cock or if he wishes he had a big cock.  It is all mental strengthening of his submission.

Increasing submission let's you push boundaries further out and increases his devotion to you

Your used panties can be a gag, a hood, or force him to wear them.  All around submissive device