Recommended training for processing inquires/applications to avoid duplicates?

We have a new person in a new role as Admissions Manager, and we want them to own the admissions process. They're new to the software and have been thrown in with very little training. The immediate problem is duplicate records being created when they're processing inquiries. I can sit them when an inquiry comes in to walk through matching records properly when potential duplicates are flagged at processing, but this isn't ideal and practically may not happen when they just quickly move through processing.

If I can point them to training, that would be a good base and I can fill in any gaps that it doesn't cover. I haven't seen anything specifically about processing/avoiding duplicates, other than this Inquiries and Applications BBU course, behind a paywall and I don't know if it covers this topic specifically.

Any recommended resources (preferably free!)?