Yes you can use it in a foam gun. Most foam guns have a 32 oz. container. So put 3.2 oz. of Hydrofoam and fill with water. Foam one section at a time, from the top down. I also spray a little from the gun into my wash mitt. Rinse well, repeat on next section.
Hydrofoam works fine on top of Reload. No issues at all. The only thing that you may see is because the surface is so slick from the Reload, the foam may slide off very fast on vertical surfaces. In this case, spray it into your wash mitt, spread, rinse, repeat.
I've tested Hydrofoam as a stand alone and it lasts 12 weeks on my un-garaged daily driver before I see any changes in water sheeting.
Basically by topping Reload with Hydrofoam, your maximizing the lifespan of the Reload, because you have another layer of protection on top of it now with the Hydrofoam.
