Click on the instance icon on a post, it'll take you to the instance page. Across the top will be several options. Scroll over to "block" and click that. It seems to take effect the next time you open or refresh Lemmee.

Edit: I should add, I have Sync, not Thunder, but it might work in a similar way.

Why wouldn't you do a Brazilian at home? I used to do it myself for years, it's totally doable

Don't forget a whetstone for that knife!