If you brush Microsol on the surface while the decal is soaking, it'll give your ham hands plenty of time to move it around to reposition.

The key is a gloss surface (Future floor finish is the best imo), which with the microsol allows for both easy movement and eliminates trapping air underneath (silvering). Then you float some Future around the edges with a brush and it'll even the surface. Once that dries, you can go over with any clear and the border of the decal will be invisible.

With Microset, you can get a decal to contour to irregular surfaces as varied as zimmerit. Jusy don't touch the decal until it completely sets. As a matter of fact, don't even look at it. Just walk away for about 8 hours. In a few minutes after brushing it on, the decal will wrinkle, bubble and become a hideous mess. You'll swear you just blew the scratch spent on the decal and solution, time spent on painting and ruined the whole thing. You'll decide the only course is to hunt down the bozo who recommended it and make him repaint the entire model. If you put that all aside and come back later, the stupid thing will be magically flat and snug.

But, the absolutely single most important thing for any decal is a gloss surface to start.