If I take my spoiler off to clean under it, how is the best way to seal the holes back up when I put it back on.

just keep the original rubber gaskets.

i did mine like 2 weeks ago, i kept the rubber gaskets and i used some clear silicone as leak insurance

OK, I guess mine are kinda squished up so it looked like some kind of putty or something.

well i just installed my spoiler and i used the original gaskets and added some clear silicone around the bolts and a little on the nuts to be safe...

Any Silicone/rtv will be fine.

Like most gaskets.. it was designed to be applied dry.

Toss it on with just the rubber gaskets. If it leaks..then add your silicone. Meanwhile..all you are doing by adding silicone is making future removal harder.

i took mine off and cleaned under it and then i got some washers to space it up a bit. as to not get dirt stuck under it as much...i used an old peice of a tube that i cut to fit the washers and it hasnt leaked.. i did this about 3 months ago.