For variety, a shift in perspective, or if one of you is an anal beginner, get the top to lie back and relax while the bottom rides.
It’s a way for the bottom to feel in control, and to be in control of how he is penetrated. He can go down gradually, take the full length at the rate he wants it, and go as hard or as slow as he wishes in any moment. He can masturbate himself as well while he’s doing it, or have the top do that for him.
His movement might be straight up and down, propelled through the knees, or use a gentle, rocking motion to enhance the sense of fluency and lower the impact, the sensation focused here on the prostate.
He should ride him to pleasure himself. If at any point the top wants it harder, the bottom can hover while the top thrusts upward from below.
It’s important for the bottom, who might be unused to setting the pace of sex, to feel confident doing what he wants, and to rest assured the top will be having a good time too, if one slightly different from his usual experience.
Keep it up to the end – or if the leg muscles tire and the bottom feels he’s done quite enough work for one day, keep yourselves plugged while rolling over.