I've done this many, many, many, many times.....so do the same thing.
Start off w/ getting this thing to ONE spot it will sit at for the whole process. I always use 4-6 5gallon buckets. Theres always enough sitting around to raise these up to working height. 2-3 buckets on either side where it will mount to the car. Once you have two stacks of 5gal buckets 2-3 high, place a rattle can on the top of each and move them around so you can put the spoiler on top of those. This gets the spoiler well into working height, so it won't need moved, and you can still paint the underside of it WITHOUT moving the spoiler. (The only time you'll need to move it is in Step3)
*Take your time*
1) Light sanding: enough to take away the shine (320grit probably) Dust off, I like to wipe down w/ xylene, you can probably use a thinner or anything to clean off oils, particles, etc.
2) 2 light coats of primer w/in 10min of each other, a 3rd 10-15min later....make it a little heavier but not too heavy to run/sag.
3) Wait, check the dry time to worth w/ the stuff. I like to do this at the end of the night to let it sit. Next use some (400grit will probably do) and just LIGHTLY smooth the primer out. You don't have to do much and if you do you'll notice you go right thru the primer to the paint again where you started. Just very lightly, it may not even look like you're doing too much to it. Clean the spoiler again w/ xylene or whatever like the first time to get the stuff off it again and move it back on top of the cans to paint again.
*Alright, by this time you have a smoothed out coat of primer on the spoiler.
4) I like to use an adhesion promoter, they have them in rattle cans so find it. Helps everything stick evenly and no bubbling or fisheyes. Lay on a couple thin coats of this. You don't need much and can put them both on in 10min. Wait, I think 10-20min will suffice, now...
5) The spoiler should be ready, get the black out and go to town. Key to using rattle can is light coats, move at the same speed, and try to do shorter strokes. I usually in total will get 4-6light coats on one to cover everything, it will look uniform and smooth by this point. Let dry for 30-60min and clear coat.
6) Esentially its the same thing as the black, but I even coat lighter 4-6 coats. Just keep doing light coats until its smoothed again. 4-6 will suffice.
By the way, all of these coats I do 5-10min apart (These times really depend on your working environment. I'm lucky enough to be doing it in the same temp area everytime.)
7) Let dry, I usually won't touch it for 1-2days just to make sure its completely cured and solid. Do it any earlier you get preemptive on handling like me and want to install it right away, soemtimes its not completely cured. Just wait the 1-2 days.
Sorry for the long write up on this, seems so simple, but you can make it look professionally done. If you do it, do it right, don't half-ass it. Hope that helps. (Yea I know....you're thinking....this long of a write up for spray paint? Whos the idiot that did that?!)
