I use Montreal Steak Spice and Hy's Seasoning Salt together. I tried a few different things over the years, but always came back to this simple combo. Don't put much on, but make sure the entire thing is evenly covered.
Taking this image, randomly from the internet:
I would use less Montreal Steak spice and make sure it isn't all clumped together. Then sprinkle on a little Hy's.
It doesn't need to sit long. I normally rub it in good, so it doesn't fall off all over the place, and then go start the BBQ, then when it is hot, throw them on.
I never use BBQ sauce or marinades on the steak. Maybe a tiny amount of HP sauce, but that depends on what the steak is with. Steak, Veggies and Rice with the juices from the steak mixed with HP on the rice is pretty good.