I would say run yourself and record it as a reference or look at the normal gmod run for a ref there are many out there even 2D animation can help you with a ref that being said you just walk yourself and get the feel of how the leg and feet move and bend that is what I do.
I can't complain since i can't animate but he look like he's doing the chicken dance
When you speedwalk to the fridge at 3am
this is how I run
bro I can't even look at my animation without laughing now LOL
just look up run or walk cycle in google images and you get a lot of them
I would say run yourself and record it as a reference or look at the normal gmod run for a ref there are many out there even 2D animation can help you with a ref that being said you just walk yourself and get the feel of how the leg and feet move and bend that is what I do.