My oldest brother told me this is what our Dad did for all five of my brothers, and I passed the information on to my husband to use with our son (he's 14 now).
Your husband will best teach your son, because he knows the "feelings". There's nothing preverted about this, but he needs to "see" his Dad actually using the potty. This includes having a bowel movement.
My Dad had my brothers stand on his shoes, in front of him, to elevate them to aim correctly in the commode. Mom kept a box of Cherrios in the bathroom and a few were thrown in the water for them to aim for. THIS WORKS!!
Make it routine to go to the bathroom first thing in the morning. You'll notice that he has a little erection, RUN to the bathroom.
After drinking liquids, before or after a meal, about 15-30 minutes, say to him "Baby, let's go try to peepee in the pot." I would tell my son, if he said that he didn't have to go, "Let's try and push out the poo-poo/peepee." Worked for him.
TAKE THE DIAPER OFF. Let him choose his new BIG BOY under pants, just like dads. Ok, dad may not wear Diego or Big Bird but he can wear Spiderman, Batman and Sponge Bob. OFF WITH THE DIAPER, it'll hamper all your efforts.
Please remember that Mom's and son's use the potty differently. I had a girlfriend who put her son on the potty for a hour at a time, only to have him stand up and go all over her. I thought it was hilarious, she didn't get it.
But I stress your husband's involvement. My husband told me that our son saw him use the urnial in the "Big Boy's room" and he was hooked. Of course Dad had to hold him up, but he did it.
Good luck.