Very stiff front suspension

WD 40. What a joke! It's not a lubricant at all.....but slick marketing made it the number one seller. It was originally designed for removal of moisture in aircraft ignition systems.....hence it's real name....."Water Displacer". If you want to grease the bushings, I would use a rubber friendly grease designed just for that purpose. The WD 40 was probably gone in an hour. PST or any of the suspension parts houses would have what you need.
It was also used by Nasa to keep one of it's rockets from rusting