TheModeler
Technically,the title says it all.I'm new to modeling,but I just use water for my waterslide decals to apply.Why do you really need all these Decal "Setters",and "Softeners"?
Remember that a decal is a color deposited on a carrier film.
Water dissolves the adhesive that holds the decal to the backing paper, but it doesn't really dissolve the decal itself.
Setters and softeners dissolve it, which is how they help get it to settle down on a surface. And the difference between them is how hot they are. Setting solutions are hotter than softeners, but they both dissolve the decal.
And as you go on in the hobby, you'll find that not all brands of decal are the same. Some brands are known for being thicker than others, for example. They usually don't settle down on the surface without help.