It’s difficult to get people to read things.
So far we have these:
- #testers category
- The Great Big Review and Testing Guide pinned to the top of #testers
- Link to the guide in global red banner
- Link to the guide in the Welcome Topic
- Colour-coded tester topics to make them stand out in the Latest list
- Sex Toy Tester - Chit-Chat as a place for people to ask questions
- Watching First Post to receive notifications for new ones
- Instructions in every tester OP, as well as a link to the guide
There may be some scope to add a pop-up when people post to the #testers category for the first time, asking them if they’ve read the guide - but that is currently beyond my skillset. 
Edit: Maybe you could include a link to the Tester Guide in the Welcome Message?