If you wish to soften the decal to snuggle it down over bumps or dips , and you cannot get hold of Microset —which is quite good— try the pre-chemical age treatment of using vinegar to soften it . Take a sniff at decal softeners and you’ll see why . Distilled vinegar is better than malt because it is colourless .
I would never dab at a decal with anything but a soft small paint brush cut down to half length bristles . This way , the decal never detaches to the pad of whatever you are using . The cotton bud idea is similar , but the brush is softer and achieves the same .
The advice about the Walthers stuff is good advice , I never use it since it wrinkled some decals beyond recovery . I mean a three day wait didn’t work . So I slung the stuff . And it attacked the paint , too .
Do not expect instant results with any decal softener , patience is required .
Mike