I probably should've picked up on some hints.
By the time I was moving out of this particularly crappy basement in Seattle, the concept of cleaning the place up to get my deposit back seemed ridiculous. The place was cleaner than it ever had been because the simple act of living there had kept most of the invasive species out. "So, now I'm supposed to clean it up more, just so this asshole can have an easier time renting it when I'm out and not give me my deposit back, anyway?" I said. "To hell with that."
This is a trap, and it's exactly what landlords want. The thing most people don't realize is that the owner in a lease agreement can't just return or keep a deposit on a whim -- there are laws in place to protect renters (more on that in a moment) -- and even though those laws don't usually get followed, they do end up mattering because, just like you, landlords are trying to avoid a big hassle. They want to keep your deposit, but they also don't want to end up in small-claims court. And they know that the more effort you put into cleaning up your home, the more likely you are to go that extra mile. Sure, scrubbing down your entire home with bleach and a toothbrush until you're bleeding out the tips of your fingernails isn't fun, and it's also not a guarantee you'll get your whole deposit back -- because some states are less protective than others and some landlords are the walking malignant butt-hole tumors who weird dark lawyer magic to ruin the lives of everyone they come into contact with. But, if you really need that cash -- and the more likely you are to have a shitty landlord, the more likely you are to need that extra check -- it's totally worth the effort.
So, mix some toothpaste, water, and vinegar together in a bowl to make homemade Spackle, and smooth it over all the holes left from the tacks holding up your Jem And The Holograms posters (I'm not here to judge!). Or, even splurge by going down to the hardware store and buying some real Spackle, as well as a Spackle-applier-thingy. You know the tool I'm talking about. It costs like $3.
My point is, you can be shitty at tools and still clean up some drywall.
Even if you don't get your full amount back, then at least you fucking went for it, man. At least you gave them hell.