using an acrylic varnish with RUST-OLEUM

Have spray painted the metal trim on a tile house number, with Painters Touch 2 x flat grey primer.  It is dry over 24 hours.  Can I now varnish it with a clear coat of acrylic varnish with a brush?

I have also used the same grey to re paint my mail box and want to keep that the grey too.  Will it be okay to also varnish this with the gloss acrylic clear varnish with a brush. 

Just to let you know, I have painted our kitchen cabinets and countertops with your products, plus painted our metal patio furniture.  Great products. 

Thank you,

Eileen