Absolutely, positively, yes!!! Thermal compound is a mandatory requirement whether or not the cpu and heatsink are lapped.
There hasn't been much discussion about lapping for a very long time. Years ago I lapped a Thermalright Ultra 120 heatsink and an Intel cpu. I still have the heatsink in a spare parts box. Considering the advancements made in cooling there really isn't any need for lapping. The only reason I did it was to see if I could do it. It was more of an experiment.