My experience with soaking tied shirts or fabric in soda ash and then drying, is the soda ash migrates to the surface of the tied piece and creates patches that resist the dye. The dye beads up and falls off the piece. I have heard that maybe you shouldn't let the fabric dry out completely.
I almost always let my fabric dry completely for greatest intensity. The key is to control the rate at which the dye flows from your bottle to match the rate of absorption. You need to "prime" the fabric with a little dye, then come back and reapply. Additionally, with bleeds, I have to really squeeze the dye into the fabric. Complete drying is my preferred method, although I am migrating to use of activated dyes at times.
With my method, I go through outrageous amounts of dye, but I get incredible intensity.
Steve