I like using a product called Dri-Slide, it's moly particles, suspended in a liquid carrier. The moly embeds itself in the metal pores, and reduces friction. Cock the hammer and put a squirt or two down the opening, and dryfire, DA a few times to distribute and work into the metal. The liquid carrier will eventually evaporate.
Adding a spring kit will do the most for lightening, while adding Dri-Slide reduces friction and smooths things out.