I reckon there should be a German compound noun that should fit the brief.
German is one of the best languages for one word descriptions, that are actually full descriptive phrases in most other languages.
There's got to be a word that means: 'he who teaches rocks to fly'
I'm going to go with: Steinfliegendlehrer
I apologise in advance for any upset my pigeon German may cause.
But I have to say: SteinFliegendLehrer
Sounds really good.
Definitely an improvement on 'schleuderer' - the actual word for a slinger.
Although, apparently it can also mean someone who indulges in self pleasure.
Unless that's a conversation I'm entirely misremembering

In which case I blame Uwe