Starch must be reapplied after each wash. Fabric softeners neither help nor hinder residue removal from cotton fabrics. The label on the pre-wash spray should say that the contents include petroleum solvents. Salt helps remove paraquat, but not other pesticides. Add one cup of table salt to your wash load with regular detergent.
Salt also helps remove excess detergent from the washer.
However, these finishes make fabrics more difficult to launder and must be renewed after every second or third wash. Use the longest wash time cycle on your machine, at least 10 to 12 minutes. Never use the suds-saver cycle or a cycle designed for knits with contaminated clothing. Clothing contaminated with highly toxic pesticides needs multiple washings. Check the pesticide label for toxicity level.