Welcome, Coozer! I agree with the others, this is pretty nice for a first effort. OP's are puzzling in the beginning because they are such a unique medium - I am beginner myself and my main complaint was that they simply weren't acting like I expected them to (as you discovered when they didn't cover up your pencil lines, for example).
Christel has given excellent technical advice with the above color blending. I would also follow Crabby's link to Robert Sloan's page for lots of helpful tips, as well as the tutorials both here at WC and online. The more you work with the OP's the better you'll be able to anticipate how they'll react and how to work with them.
You don't mention what brand of OP's you're using. Virtually any brand will get the job done, BUT the softer ones (usually considered "artist grade") are easier to handle and don't crumble as much as harder ones do ("student grade"). But all types have their uses. I like my harder OP's for a base layer or underpainting, then gradually moving to the softer ones for the top layers. Remember "fat over lean" as far as thin base coats with harder OP's, then heavier layers with softer ones. Another great trick I learned here is to use a workable fixative spray once you have applied a few layers - this lets you continue to add layers with help from the "tooth" you get from the spray, before the OP's get too slick to blend nicely.
Load yourself up with tools, as Christel mentioned. Tortillions, clay shapers, scraping tools (the type used for clay or pottery modeling are good), even a few stiff-bristled brushes. Thin lines are usually created
with the help of a tool, not simply drawn with a thick-tipped OP - but play around and figure out what works best for you.
Keep at it! I hope to see you posting more of your work.