The other day I was able to complete it on the first try without a single broken streak because there were a Ponyta and Slowpoke nearby and I finished on a task encounter Jynx I had left waiting. For me the Kanto event has made it much easier to complete that task.
Personally I don't understand how anyone aims with straight throws, I do it nowadays sometimes to make it less likely a pokemon stays in the ball and sometimes I miss the mon entirely.