Followup: Plaster repair

The National Park Service has published 40 of their briefs on Historic Restoration online as a companion to their printed materials.
The main National Park Service "briefs" link is
http://www.cr.nps.gov/hps/tps/briefs/presbhom.htm
There are some interesting articles there for the Historic restorer.
One of the things that I ran into (again more research needed) is that elastomeric paint is considered to be an accepted encapsulant for lead based paint if it has a 20 year warranty.