Well the only thing about mail ordering bondo, and stuff like that is how old the stock is , Bondo can dry out sitting on the shelf .
Same with Paint catylists , in time the products wont work like they are suppose to, these type products have a shelf life.

More so when the lid is cracked open.

Useing Omni SS I wouldnt think 3 quarts color , catylist , and reducer wouldnt be more then 200 bucks. But 200 bucks is high when you dont have it I guess

Have you tried your library for pin striping books ?

Spray