Once again a fun challenge. I liked that you talked about reference, I am working on getting better at using it and not basically copying it. I found grabbing tons of images and then putting them in pureref helped I just looked away from my monitor and started drawing after seeing a bunch.
Here are the 10 with one drawn over:
Sorry if they are too light too see, I just need to buy a scanner I swear. But I mean that kinda is the purpose right? To get some guidelines down. 
In an image editor ( GIMP, Krita, Photo) you can change the contrast.
But what I do is use a permanent marker. And draw over it with a firm, confident stroke.
It helps me to get better at those strokes!
I could just use my fineliners to do the overdraws from here on, I use them with drawabox and like 90% of my other drawings, so not sure why I don’t do that here. But I will try to provide better screenshots moving forward for sure. Thanks for the advice @FedPete
excellent work 
