I hunted that area years ago. We use to go up Fir Mountain Road, south of Hood River, off of Hwy 35, I think. There's quite a few big elk south of Hood River and The Dalles. Went to High School in The Dalles, so your inquiry brought back some fond memories.
There can be too much of a good thing with antler rattling.
I like to hit the horns together for a good 30- to 40-second rattling sequence and then hang them up and resist the urge to hit them again.
This works to the hunter's advantage, because if a buck has heard it, he may have been 300 or 400 yards away and he comes in and he's not exactly sure where it came from.
When finally is time to rattle again throw a slight change-up into the routine.
The second time, don't rattle as loud...