Agreed that Brasso has a pastey consistency, but not so with TarnX. I've used both, but prefer the TarnX. Applied with a small acid brush or cotton swab and rinsed off with contact cleaner or denatured alcohol from a wash bottle. Works for me...
Having used those for their intended purpose, I can say they're pretty nasty and would be hard to remove from a confined space, since they have a pasty consistency...
I prefer to use DeOxit. The stuff is marketed like snake oil, and is expensive, but I've been using it for close to 20 years and it really works! On low-signal / high impedance circuits, you want to be careful, since it is conductive. For example, cleaning the fine gold contacts on my 7000-series Tek oscilloscope plugins, I use a small strip of paper moistened with DeOxit. IMO, the spray is like using a fire hose to water your lawn, so, I prefer to buy a small vial of the liquid. The 7.4 ml vial will last you a lifetime... It has saved my bacon on countless occaisons.
Keith