Lightening My Touch-Up Paint. Does Anyone Have Any Tips?

[Minuit]

I recently bought a bottle and a spray can of touch up paint from Automotivetouchup.com. I've tested the spray paint and the color is a near perfect match for my truck's paint. The bottle paint, however, is noticeably darker than my paint (a couple shades at least.) I'm aware that this is probably because of my paint fading over time, and I want to lighten the bottle touchup paint to match it. I have a general idea of how I'm going to do this (mix the touchup paint with a lighter shade of metallic model paint), but any advice that y'all can give me would be really appreciated.