I am building a Doolittle B-25 in 1/48. Tried putting on the tail numbers. the decals came apart. finally got one side done by cutting apart and adding one number at a time. I am really afraid to to the wing decals. Any help would be appreciated. can't locate any aftermarket doolittle raider aircraft decals.

Sometimes old decals can be saved by giving them a coat of clear gloss acrylic and letting them dry in the sun.

after dry, do you just cut the out at the film edge and apply normally?

I wouldn't mess with any type of paint. Microscale makes a special decal solution designed to make your own, preserve and restore old decals. I'd try and find some if you can. Many hobby shops carry it, or you can order it from Micro-Mark or other online retailers. I believe it's called Microscale Decal Film or Microscale Decal Solution. I have a large pint bottle that's over 20 years old-- it's labeled "Decal Film" with a twisty Microscale banner-- but I've seen it in smaller bottles in my LHS. You just paint it over the old decal with a brush then cut it out close to the decal outline. I also use it to make my own decals by either printing them on my bubblejet printer, or using regular enamel paint, then spraying the decal film through my airbrush.
VR, Russ