Apologies for jumping in here but.....
I don't think you should be applying ANY lube to the bushings on your springs. I was told by a spring shop that this would inevitably result in the creation of 'sandpaper' in the bushing and accelerate wear, ending in failure. I don't know if this is true but I've never lubed them myself and never had to replaced the bushings once. My brothers 92' has just had the replacement to OEM after using the pretty ones which failed after about 40K. Also the new pretty colored ones are just that, pretty. The OEM bushings use a metal sleeve were the bolt goes through (atleast on my year truck) and spreads the load throughout the bushing reducing pinching and bulging.
FWIW
Regards, Bush'