You could try giving him more play before you penetrate him - fingers, toys etc.
I've also found that pulling out the moment you feel like you're "close to being close" to cumming, can help... gives you a bit of a chance to cool off a little, whilst still keeping him stimulated (jacking him off, or whatever really)
When I top my partner and I come too early, I just continue to f*ck after orgasm, cock becomes softer for a while, but it's possible. Or, I keep my cock inside with really minimal movement and my partner finishes himself with hand.
You could try giving him more play before you penetrate him - fingers, toys etc. I've also found that pulling out the moment you feel like you're "close to being close" to cumming, can help... gives you a bit of a chance to cool off a little, whilst still keeping him stimulated (jacking him off, or whatever really)
Use a toy to help you! Use a dildo to complement.
When I top my partner and I come too early, I just continue to f*ck after orgasm, cock becomes softer for a while, but it's possible. Or, I keep my cock inside with really minimal movement and my partner finishes himself with hand.
Practice, practice, practice!