If the log cabin is so nasty that you have to wash it before you work on it, than lay it on a sheet in the bath tub and fill the tub with cool water. Gently squish the quilt top a bit and let the water out. Let the top drain and press out enough water so you can lift it by the sheet and lay it flat to dry.
HOWEVER I recommend quilting it before you do anything to it if at all possible and not washing it. The fabrics may bleed if washed or disintegrate since some silks break down over time.