I also use Micro-Sol and Set.
Decals not sticking has nothing to do with what setting solution you are using. The glue is on the back of the decal and not in the setting solution. The setting solution simply softens a decal already stuck to your model. Yes, you can "melt" the decal to the suface for the painted on look however the setting solution is also very good at allowing the decal to conform to irregular surfaces. For example a decal of sign looks like crap on an brick wall. However, if you add setting solution the decal will soften and conform to the recesses of the brick wall giving the decal a more natural look.
I typically apply a thin coat of future to the spot where the decal is to be set, allow it to dry, then apply a thin coat of Solvent, apply the decal, let dry completely, and then apply setting solution a second time. If you add too much or apply solvent or apply too much pressure with your brush the decal will float or slide around. Then give the deal about 10 minutes to set and dry. If you chose then hit it with another applicaiton of Solvent. I typically hit my decals with two applications.
Once everything is cured and dried I then apply a top coat of Future. You can use any gloss coat you want including MicroScale's brand however you will need to check for compatability with your paint and decals.
Finally, are you applying your decals to a painted projecct or bare plastic? If bare plastic then be sure to wash your parts in soap and dish detergent to get rid of any mold release that may still be on the parts. Finally, if these are water slide decals try getting them wet and letting them sit on the table instead of dropping them in your cup and letting them float. I've found that floating decals don't stick as well as those that got slightly wet and sat on my table for a minute or two. I hope this helps.