I do not have the mother to him. I have triple antibiotic and will smear a small amount on his little butt hole. Should I not wash him that often?

I would give both ducklings some serious swim time in warm water. They can drink as much as they like and the muscle movement will stimulate the intestines. Usually if you put a duckling in water they poop. Just keep them supervised and if they show signs of "i have enough" get them out into a soft towel, dry them a bit and then back under the heat source.