Removing orphaned group permissions and event handlers

[caciavar]

I've got a site that is running 1.12.1, which has gone through a series of upgrades over its lifespan. At this point a few of the modules do not uninstall properly at all, but I would like to remove them manually.

I know that I can always delete the module folder and database tables manually, but it seems like there are event handlers and group permissions that remain.

I was curious to know which steps should be taken to ensure that a module is completely removed, when performing a manual removal. Namely, how would I remove the leftover group permissions and event handlers (just to keep that area clean)?

Thanks.