It's actually pretty easy to do without a grid, just imagine a # sign drawn evenly into your field of view. You really don't need a full grid screen, unless you are shooting architecture and want straight lines (with my TS-E, I always have the grid in). With macro work, I usually have the micrometer screen in. I don't always compose to the "rules" - there are reasons to break them (once you've learned them). My favorite is still on Hasselblad with a waist-level finder - you back away from the finder without the magnifier flipped up so you can "see" what the final composition is like without looking at details. You'd just image that as the final print hanging on a wall and see if it's pleasing, then pop up the mag and do final focus, then firing.
I do the same on my 1Ds3 - pull my eye away from the finder an inch or so and look at the image as a whole to see if my frame is pleasing, then check the corners for distractions, DoF preview for depth of field checks, then fire away.