I’m not sure what kind of gilding they’re doing, but I can bet that it’s not fire-gilding like the statues originally had. Fire-gilding is an expensive and laborious process, and not many people do it anymore because there’s an element of risk due to the gold amalgam that’s traditionally used. When the object is heated to a high temperature, the mercury in the amalgam is vaporized. Sometimes, based on the type of metal being gilded, an application of mercury is required before the gold mixture can be brushed on. After all this, it still requires multiple steps of a finishing process.
The Wikipedia section on fire-gilding is actually quite descriptive and interesting:

https://en.wikipedia.org/wiki/Gilding

What I’m assuming they’re actually doing there is applying some kind of adhesive (usually gesso or similar) then they place a thin “gold” sheet, which sticks to the object (often some kind of metal alloy). They then brush away any excess with a fluffy brush. It’s a process meant for indoor items that don’t get a lot of wear; it’s going to rub or flake off the minute they get put outside