The direction of application isn't important. One thing I learned is: Don't wipe it on and continue on and glance up and see a spot that was missed. When you go back, even a minute or so later, the coat you put on initially is already tacky and you will get an orange peel type look. After it drys completely, you can of course go over it again and somewhat clear up that orange peel look.
Just wipe it on and don't go back over an area for at least an hour or more.
BTW: My MH is white gel-coat and I didn't put Red Max on the slides front and back walls. After about 6 weeks, I noticed that the Red Max area has a definite yellowing compared to an area that has no Red Max. Having said that, you only notice the yellowing by an actual comparison to the area right next to it that is Red Max free. But the MH looks really, REALLY good. Great shine and no one will ever notice what I'm calling yellowing.