Hi Maureen,
That's odd about the lactulose. My vet has two kinds, yellow and green. The yellow stuff smells like cake mix and is banana flavored. I don't remember what the green stuff tastes like but my dog likes it, too. She is a chihuahua and only gets a dime-sized spot of it to lick up, but she's always happy to clean her dish. You have to be careful with it, it takes less than the recommended dosage for my dog. I measure it with a little tuberculin syringe. She gets .4 cc. I guess dogs like all sorts of things humans object to including excrement and roadkill. We tried canned pumpkin to regulate her and she didn't like that. She ate it the first time, then was not interested afterward.
Below I am putting a link to an article on bowel and bladder management, can't remember if I've given it to you before. It gives instructions for triggering the evacuation reflex. It doesn't seem to work with my dog, but there is someone on this message board who uses the technique with her dog every day.
I am not sure how you are cleaning your dog out. Since my dog has firm stools, I squeeze the soft tissue surrounding the anus and grip whatever stool is in the rectum through the skin, break it, and squeeze it out. All of this is done from the outside, no latex gloves required. I hold my dog in a ragdoll position so she has the benefit of gravity. Usually if I remove one piece of stool, more will come down into position. Sometimes if she has enough in her colon, she can evacuate it herself if I start it so the leading end of the stool holds the sphincter open for her to push. During those times when she is pushing she does have a squatting reflex, but not when I am pinching out one section of stool at a time for her.
CLICK HERE bowel management