One of the cardinal rules of painting or staining in order to avoid lap marks is to apply material wet-on-wet. On an interior wall that is done by rolling small enough sections that allow you to overlap the edge with the next section before the first one manages to dry. Painting wet-on-wet does not create two layers of paint, and a different colour at the overlap.
Outdoors we tend to not have large flat surfaces but boards or overlapping layers of siding. If you follow just a few boards on a deck from one end of the board to the other -- you are always painting wet on wet. If you follow just one or two levels of siding all the way from one side of the house to the other, you are always painting wet-on-wet. With vertical siding, follow boards all the way from top to bottom one, two or three at a time, no wider than you can handle to keep working wet-on-wet. On a hotter dryer day you may need to work on a single board at a time.
The two critical objectives in painting or staining outdoors is to get the material on without lap marks, and get it to skin before collecting dust. The first requires slowing down the drying time, or speeding up the application or some balance between all of that to work wet-on-wet. Hence do not work in direct sunlight -- in fact following the sun around the house is a good plan.
On the other hand if there are dusty conditions, we want it to set as quickly as possible. Then we may work in dryer conditions, even in direct sunlight, but on one board at a time -- giving us quick drying while maintaining the wet-on-wet rule.
If you paint across boards, you will always see your work areas long after the job has been finished.