No tool rest. My bench grinder isn't even a bench grinder, it's a homemade contraption with a 1/3hp electric motor and an arbor side by side on a piece of wood, with a belt drive between the two.
If you're holding the blade right, and sharpening the blade in the right direction, the grinder shouldn't be able to grab the blade and throw it.
this is bad logic. take it from injury-prone me. Set up your safety shit right.
Besides, if you set up an adjustable tool rest, you'll never have to worry about angle again.