When I used West Systems stuff outside, the blush was really impressive when the dew point occurred around 10 pm. It would gum up in a Scotchbrite pad when I washed the surfaces with soap and water. I am using MarinEpoxy now and haven't had any blush, but I only work in my garage. That being said, all epoxies, even those that are labeled as non-blushing, can still blush a little bit if the conditions are right. Everything I have ever read said that blush will impair the bond between layers and must be removed. I wipe all hard surfaces down with acetone prior to laying any new coat of epoxy or paint. If I feel blush, I will wipe it down before I start sanding. Even in the absence of blush, wiping down with acetone prior to applying anything is a good practice to get rid of skin oil, tool grease, butter from your breakfast biscuit, etc.
You don't need to let every layer kick before you lay the next coat. Let the first layer sit 20 minutes or so and then lay the next layer. For instance, when glassing the bottom, roll on your neat coat of epoxy, wait 20 min, fill defects, wait 20 min, lay your cloth, wait 20 min, fill the weave. That way blush doesn't get a chance to rise to the surface. I like fillets to gets a little harder, but I still want the weave of the tape to press into the fillet. By working wet-on-wet whenever possible, you can skip a lot of sanding and prep work and get a thinner/stronger lamination.
Nate
