So here's the deal...I just finished the first coat of primer, and in the process, used the entire can. Now, how long should I wait before sanding it and applying another coat? I figured I should probably do another coat of primer because there's a few spots here and there where I applied too much, so it isn't perfectly smooth. I checked the can, and the instructions read "within the hour or after 24 hours", which I find slightly perplexing. Thoughts?