tinted covers are gay.
as for the OP.
hopefully you haven't started yet.
if you haven't, do this
you stated you already wet sanded your tailights to get some crap off of them which is fine. since you already wet sanded them down with 2000 grit that should let the new tint spray adhere to the surface of the lens.
don't polish the tail lights! if you polish the tail lights you are going to need to strip the polish off of the tail lights in order to get the paint to stay on there w/o chipping/peeling.
the tail lights will clear up after they are painted on. after you spray the layers to your desired tint level let the tint paint fully cure.
after the tint is cured, clear coat them NUMEROUS times. you want at least 7-10 layers. Why so many layers? cause you will need to wet sand the clear coat after it is cured to remove all the orange peel that will be left behind. lets say you only do 3 layers of clear with some orange peel. you wetsand the clear down to get rid of the orange peel and you may end up sanding down to the point of the tint. next thing you know your wet sanding the tint and guess what? you have to start all over.
a lot of sanding will be required after the clear. start at 1500 then go up from there. if you can get some 2500 to 3000 the better. after your done sanding it's time for buffing it with a buffing compound. take your time with that, then use a polishing compound. after that you should have slick tail lights.
if you don't want to go thru all of that. just spray your tint on it, wait 5 minutes, spray your clear on it, install on car and call it a day.
or don't bother at all.