Brush size shortcut on MacBook Pro?

Hello! I wanted to try the brush size shortcuts in Photoshop CC on my MacBook Pro, but neither of the two methods I heard/read about worked.

1. There are no square brackets [ ] directly on my keypad and if I use the alt + 5/6 (which writes them in a text), the pipette symbol comes up.

2. If I use the ctrl + alt + drag option it either in/decreases the picture size or - if I click on the touchpad too - brings up the brush control panel, where I have to select the size with the slider again.

Any ideas how to get this working? Or is it not possible to use this shortcut on a laptop?

Thanks!