The next step is fairly simple but you must be careful not to remove too much of the struts surface when cleaning it. To clean the bearings mating surface I use a Dremel with the Magic Wand attachment and the burgundy Scotch-Brite/abrasive wheel product# 512E. Using the Dremel this cleaning task takes all of about 30 seconds.
The burgundy abrasive wheel is a 320 grit equivalent. If you do this by hand use a 320 wet sand paper, or close to it, so you do not damage or remove too much surface area. If you remove to much of the strut when cleaning you can literally destroy the tolerances and press fit nature of the bearing in the strut.
Remember this is simply a cleaning of the bearings mating surface not a sanding..