Especially for heavy confetti, parking saves me. For other folks, it's a nightmare. I hope it will save you since cross-country didn't work for you.
The first time I tried parking, the beginning of the first page was slow. It's a new technique and I had to spend time studying the chart to figure out how best to attack it. By the end of the first page, I was parking like I'd been doing it for 20 years, so don't be discouraged if at first you don't seem to be getting anywhere with it. You have to teach your eyes and hands what to do and that can be slow at first.
I use three highlighters: one color (usually yellow) to mark my progress, one color (orange) to put a dot on the chart to mark the parked thread and a third color (green) to'cancel' the orange dot if I change my mind and move the parked thread. If you work in 10x10 squares, you won't need the third marker. I work sometimes in large areas -- sometimes 40 or 50 stitches across -- and I occasionally have to rethink where I parked something.
Some folks 'park' in 10x10 squares by cross-country stitching in each square and finishing the square before you move on the to next. Cross-country each color and then park the thread in the stitch it'll be used for in the next 10x10 square. This is where I don't understand why people get confused saying they lose track of which color is which. If you park the thread in the next place that symbol appears on the chart, you know that thread goes to that symbol so there's no guesswork. When you get to that stitch on the chart, the thread is already there in the fabric ready to go, so for me there's nothing to be confused about. I wonder sometimes if folks are parking the threads in some arbitrary spot and not parking them in the next spot they'll be used. That would be very confusing.
I don't park in 10x10 squares. I let the design dictate the size of the area by what colors are in a certain area, and I don't cross-country stitch in the area. I use the parking method explained in the Scarlet Quince tutorial, going row by row and stitching each symbol as I come to it. I find it more orderly and the backs are neater because all the floaters are trapped under stitches and all the tails from the waste knots are part of the stitch's tension -- meaning the tail was there and the subsequent stitches trapped it instead of making a stitch with proper tension and then trying to jam the tail through the back of the stitches. For a single color, it's not a big deal, but when you're dealing with a lot of different colors -- like you do when you have heavy confetti -- that's a lot of tails to try to jam under the same group of stitches.
I don't grid. I don't feel the need to because parking using the method I do, I don't put stitches in the wrong spot. If I park a thread in the wrong spot, I discover it before a stitch is put in. If you do grid and you find it helpful, parking allows you to always see the grid because you never get ahead of yourself. The grid is covered when that section is finished and the section you move to next has a visible grid.
http://www.scarletquince.com/parking.php" target="_blank