A building we own had a sewer back up when it was empty and there is dried faeces remnants and toilet paper all over the floor. Any hints on cleaning that up without spending an arm and a leg to have someone do it?

Good masks go without saying... and not the really cheap poor fitting ones.

But how about those scrapers on a pole like used to get gum of the sidwalks? Then a broom and dustpan. Before a good quality disinfectant and cleaner to scrub what's left.

To add to what smoothy suggests.
Once the bulk is removed a high pressure jet washer, assuming it's possible and available, get things moving well..
As well as the industrial strength disinfectant, Jays fluid works a treat, stinks mind so open windows etc..