I don't have any source for you (don't use J#), but you should be able to set a reference in your C# project to your J# assembly, and then put a "using MyJSharpAssemblyName;" at the top of your C# code. Then you can access all your J# functions just like they were local.
Same applies for doing the reverse - set a reference to your C# assembly in your J# project, do the J# equivalent of "using MyCSharpAssembly" at the top of your J# code, and you're there. You get full Intellisense and everything.
Chip H.