I would skip the shrimp for now until he is cured. Something to keep in mind is that ich is ever present in our systems, but is dormant for the most part, or at least in balance with the system, not overtaking it, and not being killed off by it. It can come out in times of stress when it gets a foot hold on a fish, so by putting a new cleaner in there, you will probably only stress the fish out. The reason is that a new cleaner will incessantly clean your diseased fish, and in a small tank, he cannot really escape (in a big tank either for that matter). Seems like a lot of people advocate garlic, hope it works, but figure out why he has it in the first place, because he shouldn't get stressed enough to let it get to him despite the fact that they are very susceptible to infestations. The dip is a good idea, but good luck catching him, and the stress could kill him itself, so may not even be a good idea.