I use a monopod on a regular basis. More so than my tripod, which is currently gathering dust.....
I use a Manfrotto 679 stick, no head, though I do have the little manfrotto flippy head with QR.
Tilt heads are ok, I personally don't like them all that much, and if you squat or bend, you can get more or less the same range with the 300 connected via the tripod collar (I have this same lens as well)
With proper use, a monopod can be just as steady as a tripod.