Best acrylic varnish for very large canvas murals

[Creativebrushworks]

Hi, I'm working on four very large canvas murals, 9 x 17 feet each. Need suggestions on a varnish brand. Will hang in a 40' tower with lots of daylight and need good UV protection & flexibility as canvases will be re-stretched on site. All the fine artist varnishes  only come in small quantities & need to be brushed. Spraying is out, too big an area. Can I use a faux topcoat or varnish that I I can get in a gallon and roll? Have only used these on finishes and murals on walls. Any suggestions?
Also, each canvas was stretched for gessoing but had to take each one off stretchers to paint due to space limitations. Canvas wrinkles all came out when stretch & gessoed but now they're back, will they disappear when re-stretched? if interested, you can see job at facebook.com/creativebrushworks. Thanks, Robin!