I want to make a CRISPR knock-in S2 cell line, but efficiency is too low. I have figured out different ways to achieve it as:

S2 cells synchronization with cholechicine

RNase H II use in transfection mix to remove R- loop formation

NHEJ repair pathway arrest via inhibitors (not really sure)

So I want to ask how to go with NHEJ pathways arrest can we block this using mammalian DNA-PK inhibitors?