I have applied undiluted Bell Hammer Gold to the suspension shafts, but is it okay to apply Bell Hammer Metal Grease? If so, is it more effective than Bell Hammer Gold undiluted solution?

For application to the shaft (inner tube) of the suspension, the undiluted solution of LS Bell Hammer GOLD that you currently have is more effective than metal grease.
Bellhammer metal grease is best for suspension (rear) pillow balls, etc.