Piepea Pet Comb, Long and Short... https://www.amazon.ca/dp/B083M8S3JJ?ref=ppx_pop_mob_ap_share
I like this comb a lot for getting all the tats out. Then I got a slicker brush also for after the combing.
>FURminator for Cats, deShedding Tool for Cats >https://www.amazon.com/dp/B07MZDGF5M/ref=cm_sw_r_apan_i_F9196NAXNQ8MGWC4FPPD?psc=1
If you can find the older model somewhere, I'd recommend this over the new ones btw
You would most likely need to use shelf brackets meant for a sloped wall like these: