If you want to get a general sense of whether your intended task is possible with Grasshopper/Kangaroo, how difficult it might be, and the general approach that could be taken, you could perhaps post a description of the task (in an abstracted form if you are concerned about the confidentiality of the project).
From there you might be able to find someone with the right skills and availability and reach an agreement with them.
If you want to simply hire someone directly to complete the task for you, please do post a job advert.
However, in either case, it is appropriate to pay them, not just offer a vague suggestion that they might get paid at some point. Seeking 2-3 weeks worth of unpaid work seems exploitative, and is illegal in many countries.