Second of all, look at them non-sexually first, like just get used to finding parts you think look nice without worrying about cumming.

Then look at the nice ones and maybe touch yourself or listen to porn and work your way up.

sissygasm practice

quickshot practice

penis inversion, like chastity cages that push it in, or using dildos/vibes to push it in and masturbate like that.

no stimulation, try to cum from just flexing the muscles