As said before, TEL is nasty. Even in the percent or two in 100LL, it's dangerous. Pure, it's a nightmare. I would not want to be in arm's length of the stuff pure. It will poison you if you ingest. It will poison you if you touch it. It will poison you if you breathe it. Being an organic lead compound, it bypasses your body's natural ability to reject the heavy metals and incorporates nearly 100% of the lead it contains into your body. It's not at all like handling a chunk of lead metal, which isn't great, but will mostly just wash off your hands. It's volatile, so it goes up your nose. It blasts right through skin. It goes through latex gloves (but not nitrile). I'd want nothing to do with it.
Secondarily, it'd be a mess to figure out how much you need and how to mix it in effectively. Too much and you end up with fouled plugs and poor running. Too little and you get detonation and engine damage. It wouldn't be a fixed amount anyway, as the mix of hydrocarbons in the gasoline would affect how much you needed at the moment. I'd rather have the experts do it for me.