Need help with large canvas murals, varnish

[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 artist varnishes (winsor & newton, golden, liquitex) only come in small quantities & need to be brushed. Spraying out, too big an area. I've used Profaux acrylic varnish & lowe's valspar clear coat you can get in a gallon and roll but only have used on faux 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, can see job at facebook.com/creativebrushworks. Thanks!