I found the answer right here, from a post bbraun made three years ago:
However, for applications, THINK C is pretty easy. Although I'm still trying to figure out how to effectively use THINK C with Resedit created resources. It wants to compile resources from the Rez specification language rather than merge
in pre-compiled resources generated with something like Resedit. Additionally, when compiling an application, THINK will overwrite the target rather than merge in the compiled resources. So after every build, you'll need to copy & paste in
your precompiled resources by hand.
So that works. But wow, what a pain in the butt!