I thought I would update you on Coco's situation. I never was able to successfully express his bladder, and most of the many vets that expressed him had difficulty as well. Pbz and bethanecol were no help. He had a pezzer tube put in several times, but hated it. Because of the tube placement, it was extremely difficult to keep a diaper on him and he pulled the tube out at the slightest opportunity.
I read about a study on the use of low profile gastrostomy buttons for pet cystostomy, and after much research and effort, I was able to get Coco's surgeon to install one in the opening created for the pezzer tube. This has worked really well. With a little practice, clicking the removable tube into the button's one-way valve to drain the urine is easy. Plus, he doesn't mind the button at all and never pulled at it. So, he doesn't have to wear the diapers and protective onesies, wraps, etc. He's so much happier without those. The button is so small that he looks perfectly normal, aside from his bobbed tail which had to be partially amputated. We have had some trouble with urinary infections, and some bloodiness from irritation when Coco is too rambunctious, but overall we couldn't be happier with the cystostomy button.
As far as his bowels, Coco hasn't regained any capability there either, but Miralax has been amazing in helping keep him regular - it's SO much easier to administer than the lactulose. And, because of the button, Coco's able to freely go out in our large fenced yard, so almost all of his poop pops out while he's running and jumping and climbing out there. If he does get a bit blocked up, then a dose or two of bethanecol stimulates the intestines so that clears him right out.
I really think the buttons are an awesome option for long term bladder issues, and it's a real shame that more people don't know about it.