There should not be any issues with air bubles as pickguards are usually thick enough that this won't happen.
I have installed a few pickguards over the years. The main concerns are (1) that the top be clean where the pickguard is going to be placed (naptha is great at removing old adhesive residue from any previous pickguard) and (2) that that pickguard be placed in the right position as the modern peel off self-stick pickguards will not move once the adhesive side of the pickguard makes contact with the guitar top (trust me, having a crooked pickguard on your guitar can be highly annoying!). There are two techniques I have used to set the pickguard in the correct position:
1) I get a little suction cup (like one of those used to hold those small stained glass decorations on windows) and use that to hold onto the pickguard as you place it onto the guitar. This lets you position it correctly and then lower it down ubntil it makes contact with the guitar top. Then just press the pickguard in place
2) place the pickguard on the guitar BEFORE you peel the protective paper off of the back. When it is positioned correctly, use a couple of strips of masking tape to create a hinge by taping the pickguard to the top on the side away from the soundhole. With this hinge in place, you should be able to flip the pickguard over and then, when you flip it back, it should go right back to the correct position. When you have tried this a couple of times and it works, then flip it over, peel of the backing and slowly flip it back into its final position.
Hope these descriptions make sense.
Tres
Atlanta, GA
'64 D-40
'79 D-25
'06 D-40
