I have the hardest time being assertive with customer service people. I've been purchasing a few leather jackets recently and there is one good leather repair/alteration shop in my area (at least per a combination of yelp, styleforum and fedoralounge). There are two guys who work there, one of whom gets rave reviews, the other never gets mentioned. I've been back three times, and I always get stuck with the bad one. His english, to be frank, sucks so communication is difficult. And he's always uncomfortably excited (he's a fast talking canto who acts impatient because he can't actually speak much since he has to use english, if that explains anything), fast movements, rough with the jackets etc.
So, any recommendations on making sure I see the other guy?

when he does talk english, make it confusing at times like you don't understand what he is saying.

Don't make it obvious like you dont understand what he is saying at all. but like a small example is if he were to say it cost 17.99 you can say. "oh cool it's 16.99" make it awkward for him to want to talk to you and he will start to avoid you

Could you not just ring the shop up before hand and book an informal appointment with the good one? Just say, "hey, I was looking to bring my jacket in, I was wondering if *Good one's name* was available to take a look at it".

They won't say no outright, but if they say "sorry he's busy, but we've got *bad one* available" just say no you'll wait.

I do this all the time at, for example, my hairdressers where one bloke does it well and the other doesn't. So I have no qualms about asking for the one I like.

Like 7000 already mentioned, asking usually works. Insisting works when asking fails.

Al