You may wish to experiment a little, but if you are using Mr Mark Setter, you may be able to forego the Future application. Unlike most other decal setting solutions, Mr Mark Setter contains a mild adhesive and in most cases can fill the underlying surface and prevent silvering (this is the usual reason for applying Future before decaling).
Be aware that Mr Mark Setter really sucks down the decals on application (due to its adhesive properties), so repositioning the decal can be a little tricky. You can do so with a paintbrush loaded with some water and float the decal to the required position. If in doubt, try it on a test mule first.
also beware that the “softer” solution really will make the decals soft. with most decals its best not to try to move them (or even touch them for some )after applying this stuff. tho as usual if in doubt try it out on a decal you wont use on a bit of scrap plastic to see how much they will put up with before disintegrating . some of the new really thin decal will fall apart if you sneeze on them, whereas some of the carbon fiber decals ive used needed a bucket of both solutions and still had to be pressed down with a hot, wet cotton bud.
Setting solutions are wetting agents- they reduce the surface tension of the water, which aids in the decal sticking to the surface.
The softening solutions do exactly what they say- make the decal soft and pliable. If they are going down over raised detail it is likely you may need some softening agent. Softeners can be applied either while the decal is wet or after it is dried, but it does seem to work best if it is applied immediately after the decal is put on the surface, while it is still wet. However, it must be in the exact position needed, as the solution weakens the decal and you should not touch it after application, as the decal becomes very fragile.