Ask HN: Learning methods for solo entrepreneurs?

As a solo entrepreneur/developer, I find it difficult to find time to "learn" topics. Instead I mainly learn by "doing" which means I lack a lot depth and generally know enough to get things done.

What's a good method or technique to get a deeper learning while staying productive and getting things done (especially as a busy person with very limited time)?

It seems like learning things in depth is a pipe dream!