Starch must be reapplied after each wash. Heavy starching of the lower pantlegs helps form a pesticide-barrier and shouldn't be uncomfortable to the wearer. Ammonia and chlorine bleach, no. Ammonia and bleach have not been shown to assist in removing pesticide residues. Fabric softeners, no.
Studies show that fabric softeners neither help nor hinder residue removal in cotton fabrics.
Prewash sprays, maybe. To tell if prewash sprays contain a solvent, read the caution label. Salt helps remove paraquat, but not other pesticides. Add 1 cup of table salt to your wash load with regular detergent. However, they make fabrics more difficult to launder.