CHECK_BULK(MDOC) MDOC CHECK_BULK(MDOC)

real/check_bulk
run bulk quality checks

In a larger tree of manuals you maintain or care about, run mandoc -Tlint -Wunsupp, solve any issues showing up, run mandoc -Tlint -Werror, and start working on the issues found.

Don't attempt this with the OpenBSD base system, almost no such issues are left in OpenBSD, and those few that remain are very hard to resolve. It is very unlikely that you can come up with any useful patches to the OpenBSD base system in this way.

Don't be shy to use find(1) or scripting as required to quickly and efficiently get at the files you need. On the other hand, don't waste your time devising elaborate frameworks right now; this tutorial is about manuals, not about build systems!
Refrain from large-scale patching until you are really sure what you see are large-scale errors in your tree and cannot reasonably be solved in other ways, for example by improving mandoc(1). For this exercise, communication is of particular importance, there are people around you can talk to!
If you arrive in a state where there are no more errors, you can proceed to look at warnings.
September 26, 2014 bsd.lv