Barrel Adjuster Strategy - What's the best way to use barrel adjusters? I was taught that barrel adjusters are to be used as an on-the-road way to adjust brakes or derailleurs. I think the exact quote was &quot;Leave the barrel adjuster for the customer to use on the road&quot;
When in the shop, at home, or whatever use tools to adjust brakes using cable tension and the cable anchor. Even with index shifting - don't use the barrel adjuster to remove obvious slack.
When maintaining a bike:

Screw the barrel adjuster all the way in - brakes or derailleurs.
Adjust the brakes using only the cable anchor and cable tension.
For indexed derailleurs get the cable tension right using the anchor bolt and then do fine tuning with the adjusting barrel

Are there alternative strategies for using barrel shifters?
I think you've described best practice for a couple of reasons. Firstly, cables will not tighten themselves, only slacken, so you provide the greatest adjustment to the bike owner; they have the full thread of the adjuster to use. Secondly, the only adjustment the owner can make in the first instance is to tighten the cable. The uninitiated rider can't slacken their own cable by mistake. Thirdly, if somebody else sees your work, if they notice this detail they will see it as best practice too and see that you took the care to get this right.
Reasons to do otherwise, that I can think of are if it's your own bike and you want to make adjustments in either direction because you know what you're doing,  or if you are instructing someone remotely, such as online, you can tell them to set it halfway to begin with, which is a little more forgiving of their skills in setting the tension correctly.
That's it really, your options are to wind it all the way in and then set up the cables, or to set it not all the way in to make use of the adjustment.
Sometimes when setting up a particularly cheap component, there is so much flex in the brake for example that fine tuning without using the adjuster is a bit of a pain. But those should be rare examples.
It is fairly basic procedure to set up a v-brake or cantilever caliper such that it has good braking lever travel and you can also release the noodle or straddle wire to open the brake up and remove/insert an inflated tyre.  However, if one finds this difficult to achieve, then setting the barrel adjuster halfway allows one to slacken the cable to remove the wheel. Sometimes noodles are difficult to un/hook if the cable is on the tight side.