My experience for a prolaspe is as follows.
We had a runner drake who prolapsed.
We kept him separated and on straw.
We washed and coated his phallus with Neosporin daily. Tucking it didn't work.
We did this every day for weeks until the end of the phallus started to dry out and die. At that point, we used sharp manicure scissors to snip off the dead flesh.
Eventually he was able to retract part of his phallus and we stopped treatment. With retraction, the remaining phallus was kept moist and therefore didn't dry out and die off.
Of course, the duck was a pet and the vet was very expensive and she told us over the phone that this was all she could recommend short of making a purse string suture around the vent to hold it in.
The removed part never will grow back but the drake was still able to mate as the phallus is a long tube. He recovered fine. The phallus is long enough to get the breeding done successfully.
It is recommended not to breed prolapsed drakes for show quality ducklings as this is thought to be hereditary, though not a definitive conclusion.
Some recommend culling and just removing from the gene pool.
Also you can do nothing,. Often the drakes goes along fine, but alternatively, can get infected badly with the drying out causing scabbing with peeling and exposure of open flesh to the bacteria in the droppings.
The treatment you choose all depends on you and your intent for the drake.
Good luck in treatment.
