Moisture will turn varnish cloudy. If you wet sanded you can either wait longer to dry thoroughly OR wipe unvarnished surfaces with acetone to dry chemically. Acetone has a very stong affinity to water so it will suck up all moisture and float it away when it evaporates. We use it for this reason in the lab every day. I use it for the same reasons at home when I am prepping the kayak for epoxy work or varnishing. Never use acetone on varnished surfaces, though, it'll dissolve the varnish or at least soften and lift it from the surface it is applied to.

Robert N Pruden