I have used polarizer’s to shoot bright subjects in full sun light, but mostly to slow the shutter while still maintaining the depth of field that I wanted.

For that long glass, you'll have to get a small circular for the 300 (I think canon has a rear filter holder) or a screw on type for the zooms. . . Buy good quality, the cheaper Hoya (even their pro stuff is junk) are not good investments. Buy nikons or B&W's - they hold their value very well! The cheap one's WILL come apart on you and they will do so at the most inopportune times! Also, the thought of having a thin polarizer is attractive, but make sure you can put a REAL lens cap on it, otherwise you will have to rely on those cheesy friction covers that always fall off!!!!!!!!

I'd try it, what can you lose!

By the way, I’m back early. I came up empty but I’m headed back out in a bit to give it another go in a different area!