You should do at least 10,000 prostrations to the Thirty-five Buddhas if you can. If not, do as many as you can manage, and then do the remaining prostrations by putting the palms together and visualizing many bodies doing prostrations by reciting the Thirty-five Buddha’s names. The last buddha’s name purifies particularly the negative karma created with the gurus, so recite that not just once but five times. I did mention about this buddha’s name in the past and some students recite that name three times when they do the prayer, but you can recite it five times.
It’s best, excellent what you did, even purifying right away by reciting Vajrasattva mantra. First recognizing the mistake immediately, then purifying with Vajrasattva is excellent, not taking much time. Then finally you did confession to me, so that’s an excellent thing to do.