I have my own method for this and I'd like either confirmation that it's an acceptable solution or a reason why it's not and better alternatives.
The reason I'm framing the question like this is because I like my method. It's convenient and it allows a practically unlimited amount of force to be used. (A lot of the articles I've read say that lifters sometimes need to add more force to get their mobility to change, due to having stronger/harder tissues.)
My method is to lean forward against a wall with my feet some distance behind me and flat on the ground. The greater the distance from the wall, the more the ankle has to bend to accommodate the movement. If necessary, I move my feet further back and/or push against the wall hard enough to feel the stretch in the back part of my lower leg.
I definitely feel it stretching my Achilles and calf, but my concern (leading me to ask about it) is that it may be leaving out other tissues that limit ankle dorsiflexion.
As far as goals go, I want to be able to squat to depth without having to be forced down by weight. I can squat with reasonably good form with weight, but I can't get close to parallel (without my heels rising) with just bodyweight.