A few interesting points from their website:
There is not much difference in the formula between the Patina Green Antiquing Solution and the Rust Antiquing Solution and as it is the metal that determines if you get a rust or patina finish you can safely use the Rust Antiquing Solution as a substitute for Patina Green should you be working with both Iron and the other reactive Metallic Surfacers.
On real copper / brass / bronze we often find that the Rust Antiquing Solution which is slightly milder then the Patina Green Antiquing Solution produces a more predicable green patina then the patina solution
This implies that one can use the Patina Green solution instead of the Rusting Antique Solution to produce rust 'quicker' since its stronger.
This one suggests it may not be possible to spray this stuff at all:
Metallic Surfacers require the widest tip available. You may find the Iron Metallic Surfacer too chunky to successfully spray. For best results use an airless sprayer.