Hi Mike-

I have a beginners tutorial on strumming, with a segment specifically focussed on upstrokes. Even though it is named "acoustic strumming", the principles apply to electric strumming as well.

While it sounds like your skills may already be a little more advanced than this tutorial, it might be worth going back to the basics for a minute to see if you can nail the technique. Once it clicks into gear, you should be good to go.

Here is the first lesson in the tutorial, just to get you started. It's the second lesson in this series that introduces the upstroke.
http://www.guitartricks.com/lesson.php?input=11463

Keep us posted!
Best - Lisa McCormick