You can grease rub your frame then spot spray with FF or blasters surface shieldIt
Woolwax Undercoating 1 Year Update
Oil Undercoating Spray Gun
Is anti rust coating required to new car? - Quora
Underbody treatment / Anti-rust coating for the car - Page 19
Automotive Spray-On Rubberized Undercoating Material, 1-Gallon RUS-1020F6 : Automotive
High corrosion resistance. Completely Dries with a Permanent Tacky Coating to Assure Flexibility in Low Temperatures. Excellent sound deadening qualities. Manufactured under ISO 9002 certification. Easy application. Quick drying. Does not run or drip when applied with gun 1 Liter Covers 25 square ft. Apply on clean and dry surfaces only. Do not force dry. Sprayable vehicle undercoating offering durable rust protection to the undercarriages of cars, trucks, trailers, and RVs.
Tekton44 Undercoating for Cars, RVs, Commercial Trucks Black Undercoating Kit (12 Liter Cans + 1 Spray Gun + 1 Spray Wand)
RP-342 HEAVY Military-Grade Rust Preventive Spray
Rust-Oleum Stops Rust Flat Black Textured Spray Paint (NET WT. 15-oz) in the Spray Paint department at
Surface Preparation and Coatings for FRP - KTA-Tator