I'd be leery of using anything called "Slick 50". I'm somewhat surprised that they are still marketing products under that name. Does the name still have favor with the general public?
Belial, I never recommend people use any stop leak products, especially in cooling systems. Not only do they clog pinhole leaks, they clog all the fine internal passages in the cooling system.
I rarely have a radiator last more than 10-15 years before they need replacement, regardless of the fact that they see regular maintenance as prescribed by the manufacturer. I recommend you replace the radiator instead of adding those products in the cooling system. Try eBay for some inexpensive replacement radiators.