Hi there!
The opinion here is all correct. Another serious reason for either taking puss to a vet or a groomer is that "Blowfly" just love to lay their eggs in the cats "mat" and the larva then feed off puss, giving your critter a horrible infection . Using a "Frontline Spray" helps in prevention after mats are gone and coat is clean.
I have two long hairs, Rufus and Harry, and they are brushed everyday. I'm terrified of them getting blowfly as I saw it and it's affects once while working in an animal shelter.... many Moon ago!

I wish you the best of luck, and wait for your update.

Rufus and Harrys' thoughts are with you !>^..^< !