bp789,
My confusion is with being a "Practicing" Hindu and an atheist...or rather how would they practice their faith. Theist Hindus practice their faith through means such as puja, worshiping the murtis, and going to the temple, etc, and the goal is to attain moksha and to eventually be reunited with God. But how would a Mimamsa or Samkhya (two atheist schools of Hinduism) practice their faith? I couldn't find much online about Mimamsa and Samkhya practice in depth. Does it just consist of practices like meditation? What is the end goal of their practice (do they also want to attain moksha)? Is Mimamsa or Samkhya Hinduism essentially Buddhism or Jainism except that they believe in the Vedas? But how would that make sense since theist Hindus believe the Vedas are of divine origin, while Mimamsa and Samkhya are atheist schools, yet they believe in the Vedas?
The Mimamsakas 'practiced' Hinduism through participation in elaborate rituals laid out in the Karma-Kanda section of the Vedas. The aim of life in Mimamsa is the attainment of heaven through ritual actions dedicated to the devas. In Mimamsa, there are devas, but there isn't an Ishwara- the vedic texts are divine but they are unauthored by any being, human or divine (this view applies to the other orthodox schools of Hinduism, also).
The Samkhya school sought liberation through a philosophical enquiry into the nature of the self and the world. Through analysis of the self-Purusha, and the world, Prakriti, there arises the discrimination of their dual natures, and thus their untanglement, whereby the Purusha is freed from bondage. Samkhya philosophy became incorporated into the orthodox system of Yoga, which is theistic, thus Samkhya-Yoga accepts the existence of God, Ishwara. Both the Samkhya and Mimamsa systems of Hinduism accept the existence of supernatural realities, an immortal self, and the absolute authority of the Vedic texts, thus they don't really conflict with the overall trend of Hinduism. I hope this helps.