Either way can work. The only problem with thumbing, is that you may slip on the spool while setting. To me, getting the hookset is extremely important. Without that … the rest won’t matter most of the time.
I leave the reel engaged at boatside … immediately following hookset, I spin the drag back. As long as you are aware to do this immediately, there is plenty of time to get it down as muskie initially react by just shaking their heads.