First of all, is it a liquid sizing agent or liquid starch? Starch is completely the WRONG product to use to condition and soften fabrics. A sizing agent provides some conditioning in the final rinse to restore hand and texture, followed by proper finishing of the fabric. Starch on the other hand requires, or at least should, finishing on a press or iron regardless if its liquid, spray, or run in the rinse. Although I suspect if its diluted enough it could provide some lite conditioning, but applying heat from a tumbling dryer would yield results far less than what the product was intended to do.