Not really clear on what your concern is -- accuracy of the cut blocks, distribution of the scrappy fabrics evenly throughout the design, keeping track of the numbers required?
It's generally a good idea to do a sample block just to be sure that you aren't cutting all that fabric with some mis-read of the pattern or directions -- easier to correct something before you have all elventy-billion pieces cut.
As for the scrappy aspect, I go for the random with rules approach -- so I put all the pieces mixed up together in a pizza box (which I prefer to a baggie as it allows me to keep them flat and organized) and I pretty much pull whichever piece is next, except there will be rules specific to the project, so for example I will say -- no two pieces the same color and no repetion of the same pattern from a different colorway within the same quadrant of the ring-- just for an example.
Then when I have about 80 % of my blocks pieced, I put them up on the design wall and arrange them until I'm happy with the balance of color -- at this point I can tell if I need to be careful to do the remaining blocks with any special considerations -- needs more blue, or need to have a block which will work in that one awkward spot, and I piece my remaining blocks to fill those gaps. This is also a good point at which you can take some pictures and spot mistakes or poor color or value distribution. I like viewing in greyscale, and also checking on a computer screen-- it's amazing how many little booboos that are somehow invisible when you have the project directly in front of your face for days on end will suddenly reveal themselves in an altered format like a computer screen.
Another thing i often do is to cut enough pieces to make several extra blocks. That way, if you have a piecing mistake, you can let it slide without having to pick out seams. I find that for myself, if I have to pick out seams before going on to the next step, there is an increased risk that the project will languish in my UFO box. And the extras are great for making a coordinating pillow or bag-- and also serving as a sample piece on which to audition thread and quilting designs. When you are going very scrappy, it's a nice thing to have adequate variety from which to assemble blocks.
Hope that helps.