One thing to note about Garcia v Boxer - the locks on the boxer involve a thin object to press down on a button within one of two slots to allow you to turn the lock. I use the ends of my Leatherman micra scissors. The Garcia locks are simpler, you use a quarter or back of a knife blade. The little tab on the Garcia lid is not as durable (or doesn't look like it anyway) as the tab on the Boxer lid.
I have the smaller Boxer - it's a nice little can. The Garcia has a narrow opening in relation to the can, the Boxer is a little better/wider. I actually like the locks now that I'm used to them.
You get better at packing the cans with practice. I am a fan of Bearikades, the rental process is seamless, and getting the can in the mail a couple days early helps you figure out how to pack it. Things like couscous, oatmeal, granola, trail mix, drink powder mixes, instant potatoes, etc that can be put in ziplocs so they flow into every nook and cranny will be better than freeze dried vac packed bricks, bread, crackers, etc. Salami and cheese slices and tortillas/flatbread will slide down the inner walls and take very little room. I usually stuff ziplocs on end, vertically, down into the can, and put clif/lara bars in between until I can't get anything else in, then add layers of other things on top. Freezer bags (pint and quart) are more durable than sandwich bags (abrasion will put holes in weak bag seams which will give you a lovely mix of tang, chocolate and oatmeal crums in the bottom, mmmm).
Coffee grounds will make everything in the canister smell/taste like coffee. (Extra fun when you put in blueberries, oatmeal, some Nido for creaminess... and end up with coffee blueberry oatmeal. Blech.) A vac seal bag will hold in odor where freezer bags will not. I use scissors and make small odor proof packets out of foodsaver bags when I want to take fresh ground coffee... or get some Starbucks Via, which saves space over the grounds, but [coffee snob] isn't as tasty [/coffee snob].
I use the can a lot. :/ I love the Sierras, the bears love your food....