Despite the "rub on, wipe almost dry" repeated application of my favorite: Homer Formby's modified tung oil," there were times when I'd get some rough areas. Usually it was grain that had kicked up or dust that settled into a particular area where I might not have wiped it down as well as I could.
In either case, I preferred to first flatten the area with 1000 grit wet/dry paper and water, using a wood block backing for rigidity. The stuff cuts a finish fast, so it takes a light hand. However, the resulting dull area can be recoated with the Homer Formby's to get a bit more gloss, then the entire piece rubbed out with the 0000 steel wool and Johnson's paste wax.
The steel wool conforms to the finish's topography and doesn't flatten it out as easily or as well as the light sanding. OTOH, the conforming nature of the steel wool lends itself to a more uniform overall finish after things are flattened some, since it'll reach down into the lower areas where the sanding block only hits the high points.