What kind of paper to use for airbrush practice? I'm just getting started with an airbrush and I plan to spend some time practicing basic techniques (dots, straight lines, curves, etc.) using cheap acrylic paints which I will dilute down to airbrush paint consistency.

I eventually plan to use my (yet to be developed) airbrush skills on smooth non-porous surfaces like metal and hard plastic.   At that time, I will move up to real airbrush paints, but I hope to have developed comfortable control of the brush before then.

Question: What cheap paper types are appropriate for beginner-level airbrush practice?

I'm assuming that "low-absorption" and "extremely smooth" are traits which I should be looking for, but beyond that, I don't have a clue.

Also, if there are non-paper mediums that would serve better, (I am currently using those red-plastic disposable plates)... please let me know.
The paper you are looking for is "Bond" which has a smooth plate surface. 

You could also use Hard Press or Hot Press water color paper but that will be more absorbent.