How to use noise function/random number generator in keyframes

Hello,

I'm new to after effects, I wanted to create a simple flicker effect, and I thought the way to do this would be to add a noise function to the brightness/opacity property. I feel like my thinking is way off mark though because I searched around and no one even mentions the existance of such a function, or even mentions the need for such behaviour. I found a "wiggle" function that seems to be made specifically for position translation. Is there anyway to get a noise function that outputs values from, say, a 1D perlin noise map, and then somehow plug the output to any keyable property of an element? Even just a random number gen. If doing this ends up needing scripting/expressions, could you point me to resources that could get me started with custom AE expressions? Thanks in advance.