Originally Posted by Retro Grouch

Don't overthink this. You're already doing it exactly right. Riding a bicycle isn't nearly as complicated as some people would make you believe.

Think of your bike as having 3 different gear ranges. That's what the left shifter is for:
1 for uphills
2 for most of the time
3 for downhills and the two days each year you have a strong tailwind.

If you just do that you don't have to worry about cross chaining because you'll never do it.