The Friend Safari is driving me nuts because of this. I need Dittos to breed with, but between their lower appearance rate (at least for me-I find the other two much more often) and the catch rate trick made null and void.....it's not fun :/
What I do is use a Scyther with only False Swipe as a move and whittle them down. In turn, they can't technically kill me (until they run out of their 5 PP False Swipe and then use Struggle, in which case everyone goes down) and I have 2 - 3 turns to chuck Repeat Balls. I used to lead with someone with Yawn, but that just took too long.
Maybe I should consider training a Breloom with Spore and False Swipe, but Imposter Ditto will automatically be immune to Spore. Ha... Hmmm Smeargle...