I had the same problem with my pussy (RIP Mrs Slocombe!!) I took him to a local cattery that did cat grooming. They did it by combing out, with no sedation. It took all day mind you, but they got a carrier bag full of hair out, and he only had a few bald spots, it cost 35 quid and was worth every penny IMO.
I was seriously ashamed taking him, felt neglectful, but they assured me they'd seen much worse.