Felicity answers:
Medium and long haired cats require grooming at least once a week or fortnight to control knotting. Medium and long haired cats are renowned for tolerating grooming for short periods of time only. The last thing you want to do is stress him out. You could try brushing him for short periods then give him a treat for good behaviour. As soon as his tail twitches leave him alone and praise him. Short bursts of grooming work best and he will learn to trust you're not trying to harm him. Some cats come to actually enjoy grooming actually when they realise what you are doing. If cutting the knots out, you must be extremely careful not to cut the skin as these knots do sit close to the skin. You could use an electric razor but the sound can scare some cats. The reason some get grumpy the minute you touch the knots is because the knots are pulling at their skin all the time. I liken it to pulling the hairs on the back of your neck. If your boy is a bit on the grumpy side about grooming, it would be best to take him to your local vet, cat groomer or get someone to assist you holding him. Holding him by the scruff is the safest way for humans, but again, you don't want to stress him out. The key thing is to maintain your cats coat by grooming once a week if you can with a brush or comb that does not tug at their fur too much. The most suitable brush I find is called a Zoom Groom available from pet stores and some supermarkets. The entire brush is rubber with rubber cone bristles. It fits into the palm of your hand and works like a massage. From experience, it doesn't work on all cats, but does work well on long hair.