Fear of not knowing how much I could pack in a bear canister is one of the reasons I decided to purchase a Bearikade Expedition (then sold it at the end of the trip... the loss was about equal to what it would have cost to just rent).
But then, once I had the canister in hand, I never got around to figuring out how to pack everything into it (but purchasing ahead of time allowed me to fill it with the same amount of dead weight the food was going to be, and I realized that my back pack was NOT going to handle a 20lb bear canister... bought an Osprey Volt 75 to hold all my gear and the canister inside it).
What I did do, at home, was to package things as small as I could... repackaging things that were in packages that were simply too large (such as canned roast beef... pulled those out of the can and vacuum sealed it with an oxygen absorber) and removed excess air where I could (pre-packaged beef jerky and pre-cooked bacon, I would cut a small slit near the end of the package, push out the excess air, and then quickly reseal the package using a knife-blade-like sealer.
Never got around to trying to pack the bear canister until I was on the trail. It took two hours of trial and error until I finally figured out the process about how to organize my food to fit in the canister... don't organize it.
I simply pulled one day supply of food to the side. Everything else I wanted in the bear canister was placed anyway the things would physically fit together without leaving ANY space. I then placed the one day supply at the top of the unorganized mess in the bear canister. Each night, I repeated the process... set aside one day supply, package up everything else with no organization, but tomorrow's food on top. Obviously the process got easier as the days went by.
I eventually was able to get 10 days of food (3,000 cal/day) into a Bearikade Expedition.