he needs his anal glands emptying from time to time and currently has an infection in one of them, poor boy! Basically his poo can be a bit sloppy. i hope you are not eating!
Probably the best place to get it is a pet shop, more expensive than from a feed merchants but a big sack would probably have gone off before you could use it all.
I would recommend feeding raw bones instead - one of mine used to have anal gland problems, as soon as I swapped her to a raw diet all problems stopped (thank goodness!)
My vet recommended weetabix to me years ago when one of mine used to have anal gland trouble. Obviously not with milk and sugar, just plain. I think I used to give her one every couple of days or so and it did seem to help.
I would personally go for raw bones too, but I used to buy small bags of bran in the supermarket for my old pony when she was ill and would only eat small quantities of things. Just look in the cereals section, usually only a pound or so and packaged in a bag rather than a box.
What is he fed? Weetabix and bran is NOT ok for dogs :/ if anything it will make their stomachs more upset and more watery poo. Anal gland empty when firm poo goes through the anus and a healthy dog fed a good diet will have firm poos.
Raw feed will do the job. If not try a pet shop. We sell bran in small bags for people with horses that just need the odd bran mash. We even sell to one old lady for her own use that won't pay supermarket prices, and yes, we have pointed out to her not really for human comsumption!
You can buy 2KGs of Wheat Bran in the supermarket. Same as the stuff you get in large bags for Bran mash for horses. I always keep a small bag for my horses in case of colic and need some in a hurry and just bin it if I don't need it and it goes out of date.