Need to add more fibre to my dog's diet. Can they just have bran flakes?!

[JMSA]

Dog is a male Shih Tzu, aged nearly 10. He's a sturdy, remarkably healthy boy with the constitution of a small ox. I'm abroad just now and writing this just makes me want to squeeze his body!
Anyway, he has very recently started having trouble with his anal glands. They've been emptied several times now and he has nearly completed a course of antibiotics.
The vet said that the glands should be emptying when he poos, but his poos aren't big enough, so they're not. More fibre in his diet should sort him out.
He has been on (dry) Millie's Wolfheart since puppyhood and it has always worked well for him. What can I give him to add more fibre to his diet? Will this entail a change of food or simply the addition of something else? If at all possible, I'd like to do it the natural way rather than use something costly from the vet's.
I would have asked the vet this myself, had I taken him to today's appointment. It was a family member who went in my place.
Many thanks.

I'm thinking Weetabix might be a good one to add to his food, but then his teeth aren't great and I don't want it turning his food into cement! Separately in water would be fine I think, but how much to give?
Sorry, I think I'm just worrying a bit because I'm far from home for a couple more days. He's my world ... and my kids of course

Perhaps mix in some vegetables or brown rice? I imagine that bran flakes have added sugar, and I also think that their fibre level isn't all that high - just higher than even worse cereals.

I give mine cooked cabbage, peas and raw carrots.

I used to give my girl Pro Fibre and it worked well for her. It's about a tenner a tub from Amazon and lasts for ages

I can't remember what it's called but it's the rice skin fiber things (sorry) Phylis something. That or give him some tripe - that will firm up his poos. Or Glandex sweets. (scoot the boot I think it's called)

You are probably thinking of psyllium husk. Amazing stuff.

Our vet told us to give one weetabix a day crumbled over their dry kibble, which we then add water to. Seems to work well.

Cooked pumpkin is supposed to be the best thing - I’ve been trying it for mine but it doesn’t actually seem to have helped. I make her food and it always has pumpkin or sweet potato in (no skin) which is meant to help…

I got the vet to show me how to express her glands at home but this might not be for you, especially if infection is involved

I think I may have some of the phy ... husk stuff from when I was on a restrictive diet. I reckon I've chucked it though.
Or is there a separate dog one?!

Thanks for the replies, by the way. Very helpful.

@indianabones1

Is this the one you use?

You want to make his stools both bigger and firmer so the anal glands empty when he poos.
Try StoolRite which is made specifically for anal gland problems.
Psylium husk is good too. Not used that Pro-Fibre but they make good products so should be fine.
Bone powder, egg shells powder and pumpkin powder all could help too.

You might want to think about probiotics, prebiotics and digestive enzymes too.

Wheat is not recommended for dogs as a rule.

I bought a kilo of psyllium husk on eBay and it worked a treat. I have used oat bran too, which was equally good (not at the same time though).

Fibor worked for us - we tried adding weetabix and bran flakes but it made absolutely no difference.

I'd add grated apple and carrot to his meals rather than grains. Or just a whole carrot or some apple slices as a treat (unless it's only my dog who thinks these are a delicious snack?)

My pug had to have his anal glands emptied once and the vet said to make sure he gets carrot and broccoli for fibre and in the 5 or so years since has always emptied them himself. He also has tails wet and fry food for reference.

We had gland issue with our Border Collie, tried adding weetabix, carrots, broccoli and pumpkin, but didn’t solve the issue, I tried Pro Fibre with no success and finally got good results using Glandex, it is expensive, but once we got good solid 💩 and glands emptying regular, I now give it 3/4 times a week instead of every day, which maintains this.

@JMSA yes that's the one