I use the SD plog, I give it the once over to make sure it doesn't have any spectacular errors and use it. It's about as accurate as using the whizz wheel in my experience. It just saves time, plus if you ever saw my handwriting you would know why a printed plog is so much better.
I always mark a map up; as I've said before it helps to get the route into my head so that when I look at the pink string it's just confirming that I'm where I think I am. Plus your GPS can always go u/s and if you're flying blindly on it you will be in a world of, if not trouble, embarrassment as you call your local ATC unit for a steer. Having said that you should never be embarrassed about asking for a steer but the reason you ask for one might be embarrassing to you personally.