If you need to use that product, your fork/shock needs to have a lower service. With a sealed damper, it's 20 minutes, open 30. Air can service takes 10 from removing the shock to installing. Neither requires anything expensive, other than a chamferless-socket (garage sale/harbor freight, grind it down) and a few measuring tools.
You use something like that, and it WILL flush any [thick, good] lube you do have under the seals/bushings right out.