http://forum.fractalaudio.com/axe-f...ideo-axe-fx-ii-axe-o-matic-dsp-power-irs.html
Not a real demo or a how to but it may help you.
you can enter any value you like, they are relative value. If you want a 50%/50% mix between two IRs, 1 and 1, or 50 and 50, will work the same. It's better, though, to use values so the total is 100. Like 45, 45, 10 for three IRs for example, the third one being much lower (like what who be used for an ambiant mic or back of cab)