Does anyone here have suggestions on how I might become a better 'explainer'?
I don't know know how much experience you have with explanatory writing, but I can offer general advice based on web content writing mistakes I see a lot:
1) Avoid verbal fluff, such as qualifications and extra words. It's easier to read the previous sentence, for example, than: "Although there are exceptions, a person should not qualify everything he or she says. It's also a very good idea not to add words that are not necessary, or else an excerpt of writing will constitute what's - correctly or incorrectly - deemed in some semi-literary circles to be 'purple prose,' for what it's worth."
That kind of "clever" writing just hurts to read, but I see that sort of thing all the time. And yes, SEO writing does require more verbiage, but it should be no more elaborate than "Web content writers should avoid writing verbal fluff. Articles should not contain busy language or extra words."
2) Say things three times: the first time, say the general gist of what you mean, or specify the precise concept; the second time, say it all again in plain-speak, the third time, give examples. As in the following explanation:
Explanatory writing should reflect the needs of the person who's reading, not the knowledge of the writer. In other words, don't write what you think is interesting, and don't try to include everything about a topic. Instead, imagine what your reader must be wondering; read his mind.
In explaining to beginners how to prepare an apple pie for the first time, for instance, you might have the urge to describe the aromatic spices that go into the filling or the kinds of apples used, and all the different kinds of sweeteners possible. But a beginning baker wanting a basic apple pie recipe really wonders how to make that awesome flaky pie crust, so needs only minimal explanation of the ingredients but lots of attention to cold butter, cutting in flour, etc."
3) Watch for multiple interpretations of what you're saying and especially lack of clarity due to sloppy punctuation. People tend to be really casual about punctuation in online content, but it can confuse readers. Compare these:
"In that case are the pages we need all assembled." "In that case are the pages we need, all assembled." "In that case, are the pages we need all assembled?"
4) Write as though you're explaining the concept to a child of about eight. This is not meant to insult adult readers; it's just that we're all children when we're learning a new subject. If you look at children's books, you'll see they don't talk down to kids. They just make sure to put things in context or define them.
Or write as though speaking to a non-native English speaker. Define words. Don't use colloquial terms or terms that only people "in the know" would use - for example, don't use "in the know." ;)