Short answer
Take your grey fabric to a processing house in an estate such as Pandesara or Sachin. Approve a lab dip or strike-off sample first, agree the finished width, shrinkage and minimum lot per colour or design, and check colour fastness on the first lot.
Processing houses in Pandesara, Sachin, Palsana and Kadodara take job work on buyers' own grey fabric. Steps:
Tell us what you're looking for and we'll point you to the right market or supplier.