There are individual practices for each of these, and also practices that combine the five, in various ways. For example, the "NamCho Amitabha" sadhana is quite popular amongst Kagyu and Nyingma folks. There's an Akshobya practice that's done in Karma Kagyu 3 year retreat, or afterwards. And the practice of Kunrik or Sarvavid Vairochana is important.
More basically, these five Buddhas appear in many (most? All?) Highest Yoga Tantra sadhanas, during self-empowerment, and at other times. They represent the five families--
Each of these "families" in turn relates to the purification of a "poison," or represents the purification of a skandha, or represents one of the five wisdoms. So, for example, Akshobya can represent Dharmadhatu Wisdom, the Dharmakaya, the purification of "anger" and/or the skandha of consciousness, all at the same time. But there are differences between the correspondences, depending on what yidam sadhana you're engaged in....
The PDF from Thrangu Rinpoche goes into some detail about the specifics. It's important to understand this if you're practicing Highest Yoga Tantra in the Sarma traditions, and I think in the Nyingma as well.
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