So, here are my experiences after about 6-8 weeks, with about 20+ runs.
I’ve read articles suggesting that pressing down the big toe, while lifting the smaller toes, is a good sign of strength. However, I did not find this level of strength to be sufficient for my left foot problem, so I continued strengthening.
http://anathletesbody.com/2011/07/09/less-from-your-shoes-more-from-your-feet/
After about a year, my big toes have become fairly strong. I can now stand with my feet flat on the ground and lean forward, placing my center of mass over my big toes, and slip a piece of paper in and out under the first met. In my case, this appeared to be the minimum amount of strength needed to run with my big toes straight and engaged, and keep my left first met from driving into the ground.
Another aspect that I work on is foot flexibility. Initially, while trying to engage the big toes, I found that my feet felt somewhat stiff. So, I constantly massage any sore or tight spots in my feet. I also work on passive and actively developing range of motion. My feet are fairly flexible now, and I think that has helped immensely. I am able to flex my feet and consciously land on any part of the forefoot: lateral, medial, central, or spread over the entire forefoot. This allows me to make subtle adjustments, when needed.
Essentially, I walk and run with the big toes straight and extended. Initially, I found that extending the big toes completely, caused irritation at the interphalangeal joint. So I learned to flex the tip of the big toes slightly, so that the pad makes contact with the ground, rather than the joint. Other than doing this automatically now, I don’t actually do anything else with the big toes. I focus mostly on planting the foot and propelling forward.
With the big toes engaged, it feels like I’m running more elastically and smoothly. It feels like my legs/feet are properly tensioned springs. It feels very invigorating.
My forefoot seems much more stable, and feels like it has better contact with the ground. Like a car with an active suspension, my feet are firmly planted, allowing me to accelerate forward. My glutes feel like they are the primary muscles being used for propulsion.
As for landing, I’m not exactly sure where I’m landing, as I don’t have video or pressure pad data. I feel that most of the pressure is diffusely and comfortably spread across my entire lateral forefoot first and then the big toes, with the heel touching down last and lifting off first.
It also seems that the more I run like this, the stronger and straighter my big toes are. The skin is also more uniformly keratinized.
Over the years, my form has continued to develop. Running with the big toes straight and engaged, is the most comfortable way of running for me, at this time. It has also seemed to helped me to be able to recover more quickly. I used to run 5mi 3-4 days weekly, and I'm now doing about 5-6 days.