I wouldn't dump it.
The "best" method I found when using a brush is to do multiple thin layers. In the heat & sun a thin layer will dry very quickly....within 10-15 minutes. If you are doing a good sized area, by the time you finish the panel the section that you started with will be dry. So you don't have to sit around waiting for it to dry....you can pretty much continuously work on the panel.
I did the dump-n-spread method with a brush.....didn't go so well. If you put on a very thick layer the top will dry before the bottom will, so then you are left with a tough film of dried spectrum on top and pudding underneath it. It will dry eventually, but takes a pretty long time (days).