I'm sure it's different for different people almost all of them swap weapons using their keyboard since it's alot faster than using the scroll wheel.

I can't do it with my keyboard lol it's so awkward, so im buying a new mouse as i have a standard one, guna get number on the side of it and switch weapons like that

Yea its usually key bindings but you can set it to your comfort I think their is certain applications that help you with csgo specifically

just change your set up o fit you.

for instance i have the 3 buttons on my mouse i use.

1 which is meant for dpi switching in most games i use for switching to primary weapon fast so it's binded to primary weapon.

i have 2 just above that button mentioned above.
1 of them is for jumping and the other toggles walk on and off.

i have my spacebar binded to crouch and my z key binded to toggle through grenades(frags,decoys,flashes etc)

Everyone plays differently and finds things more comfortable, play what suits you not what suits others.

My current rank is Supreme and i have used my own set-up since i was in mg1 and it's worked wonders, im not saying use my set-up i'm saying use what is best for YOU. goodluck have fun.

It's way easier for me, because I have the Razer Naga mouse and it has a numpad on the side of the mouse which allows me to quickly swap back and forth between weapons with no hassle.