First, you need Dengar. If you have Bossk and Dengar you probably dont need this strat. Most people have probably seen it but trust me use it over the Greedo spam strat.
I literally spent 6 hours in-game of attempts and didn't get that close. After adjusting my mods for Ahnalds guide did it in 2 attempts. Some RNG yes, but I doubt it's that down to chance after the amount of tries I did with Greedo spam.