Help with multiple liveries

Hello! Im a solo designer, and I tend to make multiple liveries for one car, (ex: 5 different designs on the fipu model I have) To get to the 3rd livery (fipu_sign_3) I have to spawn 3 cars in using my trainer to cycle through them. That's the first scenario, second is this. I have a crown vic, and it only came with 1 sign file, how can I add more than just that? Also, is there a way to select a single livery without cycling through all of them? Like a menu to select them? I've tried the vehicle options in my trainer, it just dosent change. I'd rather not have to change my agency and go to the garage to spawn 1 car. (I take a lot of pictures with all the different cars and liveries) I know there's a lot to address here, but any help is greatly appreciated. Thank you!

(Sorry if this isn't the right topic)