This is what I would do. First, I would remove each spindle and clean them until they are as shiny as possible. Second, clean the bushings as best you can. Third, I would use a good quality lithium grease. Apply it to the spindle before installing. After installation, pump grease into bushing until it comes out both the top and bottom. A trick I use to get this done, is to pump the grease in with the front wheels off the ground. Many times the grease will only come out the top, due to the pressure of the wheel not allowing the grease to flow down. You can also spin the spindle while pumping in the grease.