Ultimate fighter I - close to final.. Still assessing technicalities: not all canvases are created equal!

I've been working by one hour spurt with this painting, literally. I decided to go with no "minimal" prep work (diluted acrylic medium) on regular raw cotton canvas...

Although I don't mind the result, I'm after the same surface quality as the one I obtained with my last series (large scale portraits). I need to varnish this one to determine how I will proceed with this new series. Thus far, I'm satisfied with results achieved with 50%cotton/50% linen raw canvas (light grey background).