Did you run across these two?
- CLS hydrocarbon extraction of kief tips
- Kief to Closed Loop HEMP HACKER Exctraction method allegedly high effiency anyone come across hemp hacker?
Your strategy sounds appropriate.
@beaker might suggest some sand from the volleyball court.
Only time I’ve used butane on kief was back in my open blasting days. I used a stainless thermos to do a 60min soak. Out doors. At around -5C ambient which is about as cold as it gets around these parts.
Pretty sure I used one of @Graywolf’s write ups for reference.
Wasn’t impressed with the results, but that was more likely the input quality.
Chances are it wasn’t particularly high quality if someone handed it to me to destroy at that point in my career 
Edit: I can’t find the write-up I used, but the all knowing one does give a couple of threads to pull on when asked about kief+thermos.