I've already added a touch of water to my latex paint in hopes of a smoother finish on my smooth, pre-primed, exterior fiberglass door. I've stripped the door and am starting over (long story), can I still add a bit of Flotrol I read about on this site to the same can of paint?

And, what on earth do you do when catching runs and blobs makes a bigger mess because the paint around them has dried too much to blend it out? No matter how closely I monitor it seems one always sneaks by. Sanding after the fact isn't an appealing option because these blobs are in the nooks and crannies of the panels.

Thanks for your time and advice!

Yes, you can add the Flotrol. It is a good product and does aid in smoothness. It appears to work primarily by slowing down the drying time. I primarily use it in a small sprayer where one of the problems is that the paint will accumulate and dry at the nozzle because of the low air pressure.

However, you may be having problems because you thinned the paint too much or because you are trying to put on too heavy a coat. If you think you may have thinned the paint too much, let it sit open, or in the roller pan if you are using one, for a while to see if it will thicken. Count on multiple light coats if you are having problems with runs. To avoid globs in corners paint from the corners out, not into the corner.

I agree, you can add Floetrol but not if you already added water. Adding water to Latex seems like a solution to a problem but it actually creates more issues than it solves. Sanding, priming, tack cloth and several light coats will give you a great finish. Floetrol Paint Additive