Does anyone know if using a sand blaster to de-rust/de-grime the underside of a bus before applying a protective undercoat is feasable? (we're not talking a rust bucket here, just the normal light frame rust/grime)
A sand blaster will create many future problems. Use some degreasing product, allow to soak/desolve road film/grease and pressure wash. With current temps, water should evaporate in a day or two. Buy some undercoat and cover any bare metal. Pressure washing is a tough task and may require several days. Frank