You can do the aluminum ones without the tool. I tried the steel ones too but it was pretty tough. Just drill a hole the size of the bolt you'll be using into a piece of steel flat bar to use as a handle against the rivnut, and a nut on top of that to tighten down and expand the rivnut. The handle piece protects the rivnut surface and gives you a hard surface to turn the nut against.
You could probably do the steel ones with a longer handle piece and longer wrench. Use some lube under the nut.