It’s a very good idea to do retreat for six months, and good to do some preliminaries first. It comes out for you to recite the Diamond Cutter Sutra 5,000 times. Of course, this will take some time, so start your six-month retreat like this:

In the mornings do Lama Chöpa (Guru Puja) then do a session of the Diamond Cutter Sutra. In the afternoons you could do more and your daily prayers, and then finish with the King of Prayers in the evening. This just gives you a general idea. Then after some time—giving yourself time without having to rush—do Heruka retreat.

Later, when you are continuing your normal life after retreat, try to complete 5,000 readings of the Diamond Cutter Sutra.