Re: Game
It might be obvious to you, but to potential GMs it might not be obvious at all. For example when you say 'zombie/horror filled game but may play something else' it sounds like you're willing to be very flexible, but if most games don't interest you, then you're obviously not. Some generous GMs on this site are actually willing to tailor-make games for people who want them, so I think it would benefit you to be more specific, that's all. Especially since you've been looking for so long with no luck.
As far as looking for games with 'quick RTJs', I feel like you won't have much success, unless you're looking for a game that's very basic itself. I know that I, as a GM, like to see that the players that apply to the game will be committed and are as excited about the idea as I am. No matter how long an RTJ is, you can bet that it's less work for you to fill it out than it is for the GM to run the game. I obviously won't tell you what games you should and shouldn't join as that's none of my concern, and I know it stinks to put in effort for something and then not get to use it, but typically games with really quick RTJs that will accept people first come first serve are ones that the GM has not put a lot of thought or effort into. If you want a committed GM you need to be a committed player. And if you're looking for the same types of games you could easily reuse content you create for one game in another if you don't get into the first one.
Also if you're worried about not getting in, maybe you could say something about the sorts of characters you like to play? That way potential GMs would have a better idea of whether they want your character in the game so you'd have a bit more chance of getting in after filling in the RTJ instead of taking a shot in the dark.