Tollens is super simple. What you need is a soluble silver salt (like silver nitrate or silver acetate) and a reducing agent (glucose can be used). With the price of silver today, say $30/oz or $1/gram, the silver salt will be expensive.
One of the early uses of the reagent was to silver mirrors, including telescopes. You need an actual metal to solder to. Silver paint and nickle paint probably won't work, as you have found out. There may be some conversion coatings for other metals that may work, but have no experience with them. As a last resort, I might try a mercury/silver amalgam, but if you are going to do that, why not go the Tollens route?.
John