ZBrushCentral

How change brush size and hardness with using pen?

In Photoshop: presshold alt + presshold RMB and move up/down/left/right
In Substance Painter: presshold ctrl + presshold RMB and move up/down/left/right

What’s the combination in Zbrush?

press S, release, LMB drag left or right

o, cheers. Not bad. Can I change focus shift the same way?

‘U’ I think.

If you hover over focal shift, brush size, etc, the tool tip will also display the hotkey.