I can tell you what we did with Beau, who had surgery to remove a ball from his stomach. Due to all the fluids during surgery, Beau was a lean mean peeing machine. He was also given dexamethasone. So, our Vet advised against giving any supplemental gluc. He'd had enough. I was to keep him off prednisone for 48 hours. This was to help him heal. Pred. can make healing difficult. Standard Poodles have extremely thin stomach walls. So, Beau was sutured very tightly, and our Doc doubled the amount. We even left his stitches in a week longer than would be normal following this surgery.
The biggest worry was starting him back on food. We did this so slowly. The first 2 days, he had several tblsp. of baby food only and was allowed sips (only) of water. I had to take all the bowls up, and Sam was given water away from Beau. Doc did not want his stomach full of anything that would put pressure on those sutures. Doc was also worried that he would vomit. That would not do his incision any good at all. On the third day, I began giving him canned food (a Eukanuba puppy food), and more water. He was allowed 1/2 can (they're the size of a tuna fish can) divided into mini meals. Then, the fourth, day he could have the entire can. I split this into 4 meals. By now, too, I kept the water bowls only partially filled. By the 6th day, we progressed to Hills ID. Beau stayed on the ID until his stitches were removed
Beau slept a lot the first day following the surgery. And, for most of the second day. The evening of the second day, he was in discomfort, and I was advised to give him 1/2 of a 25 mg acepromazine to help the discomfort. I really only had to do this once. Beau took a lot of watching, but he healed very well. My Doctor's recommendations for him were followed to the letter.
I reallly think it would be a good idea to talk with your Vet about giving lots of extra Florinef. When Sampson (he's the only one who takes Florinef) underwent a smaller procedure last year, I was told, again to withhold the gluc for a day. The Dexamethasone takes care of that, and I returned to Sam's regular dosage of Florinef. Too much is just that . . .too much. It won't do any good, and could give you a response you don't want like - frequent urination and possibly diarrhea.
(courtesy Cathy R)