You could use the left and right bracket keys to resize the brush? [ and ]
Also, if you have display glitches then it's lily to do with the GPU acceleration which can be switched off in the preferences. Or, you may also want to try updating the driver for your graphics card.
Thank you for your answers.
With the brackets it's takes a lot more time and I don't find it as effective as alt+right click.
I tried to disable the GPU acceleration and update the graphics card driver and the issue is still there.
I just checked them all and the only place where the brush resizing using ALT+right click works without delay is when I'm using the Liquify tool.
same and kinda annoying..
and with the brush tool i'm pretty sure it has something to do with some conflict with the eydropper brush function which is activated by just pressing alt.
for example, when using the brush, if you press alt, the eyedropper tool is activated.
this one has some delay also..
if, after a few seconds you right click, the brush size preview is activated, with some half second delay.
but, if you press alt, (eyedrop tool), then you left click to use the tool, and then you right click to resize the brush, the brush preview activates instantly..
I tried also to update to latest version of Ps CC and it's the same issue.. so it might be a program related thing.
Tried the 'PS CC 2018' update and still the same issue..