Heres how I apply my decals.
1. spray the model with a glosscaot (i use future floor polish)
2. when its dry, I cut out the detail and put into a bottle cap filled with water (might need a bowl for the larger decals.)
3. after around 10-20 seconds I remove the decal from the water with tweezers.
4. I then place the decal as close as possible to the area that it needs to go.
5. then, slide the decal off the backing paper and position it. ( use a toothpick and/or a paint brush (came from a crayola watercolor set) )
6. once the decal is in position, push out all air bubbles with a toothpick.
7. Finally I cover the decal in some solvaset and then when its all dry I seal the model up with a dull coat.