I bought a #4 smoother with the intent of using it for final prep before finishing, i.e. eliminating the need for sanding. After several projects (2 vanities, medicine cabinet doors, shaker table, etc.) I’ve come to realize that sanding is still absolutely necessary. My smoother and/or hand scraper inevitably leaves chatter marks that are visible after the finish coats go on. I even wiped on mineral spirits and used a raking light in both directions prior to applying finish. From now on I will sand to 220 or so before applying the final finish coats.
By the way, my #4 is very sharp and takes whisper thin shavings, and it is cambered. These projects were either red oak or ash. The ash seems to be especially susceptible to tearout, so I back beveled the bevel down blade to 72 degrees. Ha! I miscalculated thinking it was bedded at 25 instead of the 45, so I added a 27 back bevel. Boy it leaves a nice clean cut though. Who says you need a high angle frog?!?!