There are various methods, some spray it straight from the bottle, others thin it with Isopropyl Alcohol. You can also brush it on with a broad brush. Its self levelling properties help to hide brush marks. Some will also rub back each layer and recoat to get a showroom shine
That is not necessary if you are only going to flat coat after the declas go down.
You can use a decal softener. I have used the Microscale products as well as Solavaset. Just be aware that some softeners will turn the surrounding future a milky white colour. But do not dispair, if you recoat the area after the decls have set with a fresh coat of Future the white disappears.
Missed it by that much!....