Fred, I've found that plain old 70% isopropyl rubbing alcohol works better than either denatured alcohol or plain water alone. As Damascus says, it seems to penetrate deeper into the wood than plain water. But you need to give It enough time to soak deep into the wood, and it may take several applications to accomplish that. It is also important to remove the finish so that the alcohol can get in. The pores in the wood are the vascular system that transported water and nutrients while the tree was alive. And they will still permit the alcohol to get in if they are not filled with finish. Most people simply apply a moistened cloth to the surface, but by getting the dented area good and wet, you are then generating steam from deeper below the surface, and swelling the compressed wood more than by simply attempting to drive steam down into the wood from the surface.
It is still important to use a moistened cloth on the surface so that your dent raising iron does not scorch the wood. And being persistent with repeated attempts sometimes really pays off. I don't usr a clothes iron, but instead made several smaller dent raising irons that are heated with either a propane torch or a stove burner. The worst dents are those that result from the stock striking a sharp edge which breaks the fibers of the wood. But even many of those really bad dents can be substantially raised.
I think it might be interesting to experiment with a junk stock, and soak a dent well, and then pop it into a large microwave oven to create the steam. But it would require some restraint to avoid overheating. Once, I was using a microwave to heat a shotgun forend wrapped in tissue to get the oil out. It was working great until I got it too hot and heard a crack, and found it had split lengthwise. It glued up well, but was pretty disconcerting at the time.