With a paint brush. I would put both items in a rubbermaid tub or similar when coating, because it will drip a lot. I'd also have each elevated so it doesn't stick to the bottom of the container when the resin dries. You'll want to make sure to really slather the stuff on and not miss a single part, even if the item will only partially submerged. There is still risk of poisoning the tank if you only coat the bottom half.