Hello Allen & All,
I believe it is written up by the USDA but not sure the location. What Blane
is saying is you can always use less then label but not more than label. I
use approved food grade menthol. George is using a essential oil. The
peppermint spirits might work but are not approved method.  I don't know the
rules for Canada.
I use the 1 lb.(by weight) menthol to canola oil and haven't had dead brood.
I did get dead brood and bees driven from the hives with the 2 lb. mix from
the article. I do not measure the amount of canola and only top off the 3
lb. coffee can. I do everything exactly like the 1 lb. formula presented in
the ABJ article. In your case making a larger batch you might have to guess
at the amount of canola.
I have always used the second dose. My thoughts were to keep the treatment
on as long as menthol would normally be on the hive. I have never treated
only once and then checked. Maybe I should have. I find many of the problems
associated with various treatments we use are not successful because we do
not follow instructions and timing.  Resistance to Terramycin could have
developed because beekeepers were not appling properly.  Dose one week. Dose
ten days later.
Timming is very important in using chemicals or antibiotics.
Bob