Check for wall insulation?

Does anyone know of a practical way to check exterior wall to see if they are insulated? We'd assumed that our old house had zero wall insulation since we've had exterior walls on two sides of the house open to do remodeling and found no insulation and only tar paper for a vapor barrier but while installing a pellet stove recently we discovered that the exterior wall on the west side of the house had not only blown cellulose but an extra layer of wood and what I call rosen paper behind the clapboards. The interior walls are all horsehair plaster and wood lath so I don't really want to drill a bunch of large holes in them if I can avoid it.

I have an inrared thermometer so I'm wondering if taking readings off various points of the exterior walls, on a cold day when the house is warm, might work. Any thoughts?

Well, the easiest way to do this is with a thermographic inspection, but you will probably have to pay somebody to do this. Basically, they use thermal imaging to view hot/cold spots in your walls and and can determine where insulation is or is not present.

Here is a more detailed explanation.

http://www.eere.energy.gov/consumer/your_home/energy_audits/index.cfm/mytopic=11200