From Oldsmobile list server... Doug Ahern's (paraphrased) message on applying self-adhesive air cleaner decals.

A great source for repro decals is Jim Osbourne Reproductions in
Lawerenceville, GA  (770) 962-7556.  Jim supplies Year One with
decals.  Whenever I get decals from him I always ask him what is
the best way to apply them. On most decals, he recommends using
soapy water, getting the aircleaner (or whatever) completely wet
and putting the decal on.
I'm talking about the peel and stick foil type decal.  The decals that
go on mid 60's Olds air cleaners. The same kind that were used on
the '64 442 air cleaner element housings. If you apply these sticky
backed stickers to an air cleaner covered in soapy water, you can
work out all the bubbles and get it perfect. The soapy water will
give you ample time to smooth everything out. Sponge off as much
soapy water as you can, then let it dry.  The adhesive on the back of
the sticker stays sticky the entire time.  Then let it dry. Works
great.  I've used this advice many times with fantastic success. Jim
is alot more fun and easy to deal with than Year One.

Jim Osbourne Reproductions
101 Ridgecrest Dr.
Lawrenceville, GA  30245
(770) 962-7556

! ! Bryceman's note: It has been reported that Johnson's Baby Shampoo is the ideal soap for this because it's low ph qualities are less likely to degrade a decal's adhesive.