flat characters? Never heard of that tern before.
Hands are hard to draw, after many years of practice i hope i master that technique.
as far as human drawing and just drawing in general, with practice and time will get anyone better. I would avoid tracing an image from a photo because anyone can do that. the finished result does not entice the viewer as much as a drawn composition, if this makes sense.
as far as using software, photoshop seems the best, with a pen stylus- i figured out placing a sheet of white paper over the drawing pad helps get better lines without that slip.
I am still waking up and kinda tired from a 12 hour drawing day yesterday an do not want to type unclear advice or reasons until i get my day started.
im sure others will comment here soon!