I've just always used the grid method only I do my grid 1" bigger than finished size instead of 7/8" and trim down while squaring them up. I also use the leaders and enders method for making them with the triangle bits I lop off from making flying geese blocks (which I make using a rectangle and a square) and trim those to various sizes.
This has always worked well for me and I don't mind marking the fabric because my grid marks for the squares are usually cut off in the trimming process and the lines drawn for my sewing 1/4" away are invisible in my seam allowance.