I think I have a very weird method , but it may work for you.
I first seperate lights darks and mediums. Then I toss all of the darks on the floors so they are only a few deep. I toss to one pile all those that just can't blend looking at the pile from about 5 ft away. There will be some that just jump out screamming " Get me out of here" those get tossed in a seperate pile . I do the same for the mediums.
I then have my group to work with. Whats intereseting is the one that will not mix and get tossed out end up being a great group ...typically.
If I am not sure if a fabric is medium or dark I toss it in the next group , it will tell you at the end of the sort if it really belongs there.
I discovered this toss it all on the floor method when some shelves gave way in my sewing room . All the fabric laid in a pile , as I was picking them up I was so surprised what went with what , combinations I never would have put together had they not fallen on the floor.
Once I have piles , I pick my pattern based on quantites in each.