I'm not pro about SF but in my experience since this is body weight exercise i watch for my heart rate. Don't exhaust your self. Take it slow, as they said before reduce your resting time don't go fast. When you feel like i cant do anymore do 1 more or 2 more
To be clear about D1 (what i'm doing is)
-i do good form.
-rest no more then 45-60 sec
-close to the end of workout, when i feel cant do anymore i do 2 - 5 more reps, i don't count reps that exceeded 20 mins.
And, don't forget to post