You're welcome!
Hmmm tough decision! I hardly ever do lineart when I paint so I'd probably go for shading. It in involves both color and getting closer to the likeness of the reference.
I sometimes set myself a time limit of 10-15 minutes and do a quick sketch. It's a good practice but in the end every single little step you take will help you improve.
And thank you so much for your kind words! I still need to get one copy of Tony printed for my own wall but I'm out of frames (and money). :'D