1) remove loose material with a scraper and sand surface with medium sand paper. On drywall or plaster or concrete you can use Poly Filler or a multi purpose patching compound. Depending on how smooth you want the job, you may need 2 or 3 coats with sanding between each coat.
Have fun!...
_________________________
Bart Blainey, B.E.R.
Consultant/Journeyman Carpenter
Building Envelope Specialist
Master Renovator
provip@prodeck.org
http://www.prodeck.orgBarton Blainey (provip) specifically assumes no legal liability or responsibility for the accuracy, completeness or usefulness of any information or process disclosed. The above further expressly advises that any use of or reliance upon the information and or opinion disclosed is at your risk .