Decals need two things: an adhesive which will help them stick to the model better (especially true for bare plastic) and softening agent which will mould the decals to uneven surfaces such as panel lines, bolts, weld seams, zimmerit or cast textures.
Classic solutions involve two fluids which complicates things and makes the two bottle sets a more expensive affair. VMS Decal Set & Soften is a single, 2 in 1 product that does both jobs better by giving fantastic adhesion with proprietary adhesive formulation while being less aggressive than classic softening fluids minimizing the possible damage to paint coat.