Pest Rule and Control Management

I have dogs and they live in the house but of course it’s always nice to take them to the park and i am getting tired of washing them everytime i take them to the park. What’s the best flea control treatment I can purchase at the vet or anywhere( for the price if it’s in the range (30-60$ then it’s fine with me) I wash them like once every week or twice every week and i would like to know of a brand that will last for decent period of a time and won’t harm my pets or myself. Thank You.