I have a pattern plane with a Himax 6330-210 pro motor. I am running a 21 x 13 prop on it and the down lines are quite fast. I want to slow it down some. I use 30% brake, but I run the trim so that the motor has a few rotations at idle. I like that on landing. Best 2 blade, or a 3 blade.
Entertaining recommendations.

From your description, it sounds like you are not enabling the 30% brake setting in the ESC to be utilized. If on the ground your prop is spinning (idling) from power at full low stick then your brake is not activated. Depending on the ESC typically the brake is activated at an endpoint setting somewhere between where the ESC arms and before idle is enabled.

After arming, activating the brake can be achieved during flight by toggling a switch between different flight modes (aka conditions) which have different low throttle endpoint settings, brake vs idle. Also depending on the ESC there may be settings that influence whether the brake is activated instantly or with a user definable delay time before enabling the brake. In addition, some ESC’s provide the ability when the brake is activated to ramp up to full brake power by configuring starting and end percentages of the brake's power.

If the above is true I would recommend getting the brake to activate before changing props.

As far as I know, with all the currently-used ESCs, the brake only works at the lowest setting that you have on your Tx throttle curve,i.e. at the point where the ESC arms.
So setting your idle a few revs above that point,means that all ESC braking is lost,and any braking effect is just prop dependent.
In general, you'll get more prop braking with a bigger diameter,and to a lesser extent with a wider blade, and also with more blades of course.

Thanks Glen,
I start the prop after activation with the trim. Prop doesn't move after activation until I bring the trim up. However, you have given a good suggestion with selecting a switch to idle. I could make sure I don't idle up at start up and try that. I have a Castle ESC.

That makes sense, consistent with Glen's answer too. Maybe that is my problem, I always trim idle up before take off to help in landing, so I'll stop that tomorrow and test it.
Thanks for your help.

Ummm...

I have one of those motors on an AJ 2M Acuity and it runs a 20x13 prop, partially because of out field elevation. Not sure what percentages are used as my friend set the thing up and it works fine. As for the "idle up", we setup the ESC to arm with the throttle trim all the way down and the brake off. Bring the throttle trim up to where you get the RPM you want and then flip the switch to knock it back down and the brake engages. We always test it before takeoff.

Personally, I prefer having the brake on for landing as the Pattern planes just don't want to slow down on the rollout if the prop isn't helping.

Thank you for your information. Very helpful. Makes sense to me.

Go to a 21-12 you will notice a lot in speed it will slow it down quite a bit, that's what I use on the Himax, you will have to bump up the end points if you do

Thanks to everyone for your suggestions? I flew today and did not use motor trim. The brake worked, so that was an issue, now for the prop change, tomorrow.

A good friend of mines struggles with the brake setting as well. Like you did he brings up the trim to just start the prop to spin. However my plane I actuallly have the brake set at 90%. And when power is applied and not spinning you can just move it by hand and hear the brake work. I have an OS 110 hv esc and plettty motor. Point is you might consider a higher brake setting and have your trim set just below the prop spinning.

Also so my friend just moved up your way. Tim Pritchett. Hopefullly we will see you at one of those contests up there.