While it’s not great to scare them, it is important to brush them as if he ends up injesting too much fur it will result in a blockage.
If you’re seeing string poops, then it means he is injesting some fur. It also means it’s coming out the way it should, so don’t be too concerned!
try giving him a short brush on a high surface, and make sure you give him a treat immediately after so soon he’ll work out brush = treat.
You could also try a lint roller, although i’m not sure how that will work with a lionhead. Those sticky lint rollers are absolutely amazing on my mini lops, you can see how much fur comes out in just one roll, and it’s super quick and painless so they don’t tend to mind. The loose fur just gets stuck to the sticker.
How old is he? If he’s an adult it might be worth giving him a little piece of pineapple, which some people (including me) believe helps break down the fur in the stomach. Some people think it’s an old wives tale though, so up to you! If he’s still a baby, then it’s probably best not to give him fruit yet.