Good technique. Everyone should know how to do this. I used to do the same before I got my densitometer. Of course now days a densitometer can be found for a fraction of the price of a spot meter
On a related note, anyone needing to find 0.1 for film speed tests can use just about any meter (doesn't need to be a spot meter) and just hold the film over the sensor. Look for a 1/3 of a stop drop in the reading.