What kind of screwdriver do I need for the starwheel adjuster (2005 Prius)?

See this thread. It might help
Rear Brake Clean and Adjust | PriusChat

And this
Self-adjusters

The hole you are referencing doesn't seem to be the right one for adjusting the brakes. They should be self adjusting unless you replaced the shoes. To self adjust, do this.

"put the car in reverse, build up a little bit speed (not a ton) and apply the brakes. You are supposed to do that a few times. This will "adjust" the brakes and make them feel normal.

 

Is it possible you need to adjust the emergency brake tensioning rather than the starwheel?

 

On no account move that part of the car. Put back the rubber cover, that is the bleed valve for the hydraulic brakes.

The adjusting hole is on the brake drum ( the part you can rotate with the wheel fixing studs). The adjusting hole is on the same side as these studs and the hole has to be turned to a position near the bottom to get to the adjuster star wheel.

 

Yes Brit, you are right again. The rubber cover that you took off is a dust cover for the bleed valve. The rubber cover to adjust the starwheel is flat and is on the top of the hub. The hole on the top of this picture (not an actual Prius drum) is about where its at on the Prius





And this pic (not an actual Prius drum either but a good/close representation) shows good detail of about where it is located (note the location of the starwheel).

Here's the actual Prius Drum

When I changed out my brakes, I just used a regular flat tip like this one.

 

The instructions I gave in my post (5) are for the UK/Europe version with disk and drum setup where the parking brake is adjusted from the wheel side of the drum. The US arrangement is different in that the adjuster whole is in the back plate not the drum. Sorry for any confusion, but the part about the bleed valve still stands.

 

Good deal.

 

Pleased we were able to help.