Just a word of caution. In terms of any paint (rattle can or otherwise), even if you find yourself able to get the paint to apply and adhere, don't be entirely surprised if the color doesn't match. Speedway Blue is a VERY finicky color to properly color match - even with the factory-fresh shades. Add in a few years of sun-fade, and it's a guarantee that there will be some mismatch. Also, though you may have a factory paint code, take note that many paint codes (including Speedway Blue) have what are known in the industry as "variations" where there may be multiple shades of the same paint code. Most auto paint stores can pinpoint which variation you need based upon your VIN - but even then there will be some deviation.
Another factor to consider is the brand and line of paint. Some brands match some colors better than others. I've used Dupont ChromaSystem and BASF Diamont / Onyx HD paints and found strengths and weaknesses in each for color matching. As for Sherwin William's automotive paints, Ive actually not heard any good things about them though not from personal experience since I've never used it.
Nonetheless, I would recommend shooting paint and clear onto some sample piece and, after it all cures, compare directly against the truck to check for color match. This would also be good practice to understand your rattle can spray pattern and coating technique so that it applies smoothly and evenly, doesn't streak and doesn't leave "zebra patterns" (which a rattle can may be prone to do, especially if fired from too close to your work surface). And if it appears to color match on your sample spray panel, still be prepared to have to paint both of the lower front bumper valence panels and not just the one that's shedding paint just so that you have a hope of being able to blend your new shade of blue into the blue that's already on the truck.
