I have had better cutting success since I started using a heatmat last year with cuttings. I have my cuttings in cups in a clear bin, lid on, and heatmat underneath.
I am also using the shoebox method this year for the first time. I have been trying to figure out how to incorperate the heatmat with the boxes. Still have not figured that out yet.
But the heatmat seemed to get the stobborn cuttings started that were just staying dormant when I tried all other methods last year.