Prepping pedals when installing I am moving my pedals from one bike to another, and removing them caused a lot of frustration.  I had greased them before hand with some basic automotive grease, and the threads were still greasy when I finally go the pedals off. I made sure that I was turning the pedals the correct way.
Is there a specific product that I should be using so I don't have to use a 6 foot cheater bar to remove them later?  Should I just make a habit of loosening and retightening them more often so that they don't get too tight? Did I maybe tighten them too much when I installed them? I understand that pedals are self tightening due to the way they are threaded, but it seems that often they are really hard to remove.
Sounds like you tightened them too tight.
You did everything else right - pedals on the right side, threaded the right way, grease.
So, if you had to use a 6 foot cheater bar you might have used a little too much muscle when tightening.
According to bikeride.com pedals should be torqued to something between 276 and 354 inch pounds or 29 to 40 Newton Meters depending on the crank arm.
Campgnolo = 40 Nm or 354 in lbs
FSA = 29 to 34 NM or 257 to 301 in lbs
Ritchey = 35 Nm or 307 in lbs
Shimano = 35 Nm or 304 in lbs