Luna has always been skittish. When I first got her she was scared of people approaching her too fast, bikes, skateboards, loud noises etc. I have tried to keep her exposed to those kind of situations regularly and now she is no longer afraid. However with that being said, I cannot break her of being afraid of garbage trucks. I have tried to expose her by bringing her out in the front yard when they come by and also by trying to walk by them when we are on our walks. Nothing I do seems to work, right now is supposed to be walking time but we are cooped in the house because it's garbage day. Any advice on how to help her? Also when the trucks come by I do not coddle her, when she isn't whining or pulling away I praise her immensely but it just doesn't seem to be catching.

I would suggest keeping at it. its a long process to really desensitize a dog. Ripley it took weeks of us sitting for 5-10 minutes by the busy street to get her to not get stressed when a truck passed by. She now notes them, but doesnt pull or cower like she was. Chris picks me up at the train every day and he would just sit by the road and wait, getting her to sit everytime she stood up when one passed, and praising when she ignored them.
Trains still throw her off. There are a few trains that pass, the commuter trains arent so bad, but the heavy container trains are really loud and it completely messes her up until we can get her to a quieter street.
In short, remain consistent, and keep at it, dont give up.