Yes, I've been doing that with some of the clothing figures I've made recently. As you said, just place your conforming clothing and set up your pose. Export the clothing as a .obj, re-import it and run the scene through the cloth room. One thing to be sure to do though is make sure the clothing doesn't touch or intersect the figure that was conformed to. You'll get really weird results with the clothing twisting and bunching up if it bumps into the main figure.