We recently did two commercial painting projects and both involved repair and painting of columns. One job was in Council Bluffs Iowa and the other was in Bellevue Nebraska. The first one in Council Bluffs had columns that were not too bad. Peeling paint and a bit gouged up. These we sanded down and we used a couple coats of glazing putty on them.
The putty is a two component product. You have to move fairly fast. On the upside it sands out easily. We then prime it out and paint it.
The second project had columns in much worse shape. For these we used a commercial filler product because of the depth of the repair. Then we finished it off with the glazing putty.
When doing this type of repair work on columns it is very important to sand thoroughly and correctly. The curved nature will highlight poor sanding. We always do a couple coats of a quality primer as well.
Repairs of this type are time consuming but when done right the results are great.