I hand brush Pledge as the self leveling action of the product does not require an air brush (which I can't use anyway.) I cover just the larger area the decal will go on such as the whole side of a car but not the roof. I don't feel I need to cover areas such as car roofs or underframe where no decals will be applied. Use a clean soft very fine bristle art brush to apply pledge. I clean the brushes with IPA and water immediately after use.

After decaling I spray with a rattle can Tamiya matte finish. 
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Ken Adams
Still in splendid Shelter In Place solitude, about half way up Walnut Creek