Grooming Help

I am in some serious need of some grooming help for my cat. She has some major mats and feces trapped in her mats near her bum. I have tried bathing her my self, combing her myself and shaving her myself. The entire thing is making her hate me and me hate this whole thing. I already feel extremely terrible for letting it get this far. I am in Colorado Springs and needing some advice on cheaper groomers that can de-mat and shave near her bum. Or just some advice on how to do it at home. I have crunched the numbers and getting her a $300+ grooming is just way to out of budget for my preschool teacher income.