I've only made a few elm bows but was completely impressed with it as a bow wood. I would take it to a good floor tiller stage or even first low brace then clamp it to a caul at the handle and using a heat gun(I like to use cooking oil at this point), work out each limb making corrections. In the twisted areas use small wood wedges with a clamp or 2 to correct the twist. I usually clamp every 6" to 8", depending on the limb. Be sure to pad the clamps or they will leave an indentation. Once the bow is fully clamped I go over it once more with the heat gun and thoroughly heat the limbs then let it sit overnight before removing the clamps.
Elm reacts well to heat tempering. I do this without oil and heat to a nice chocolate brown color, clamping it to the same caul as above. I like to add about 3" to 4" of reflex at correction and tempering time. After tempering I give the bow at least a few days to rehydrate, depending on the R/H of your area at the time.
