Media blasting of aluminum frames need not be avoided, as long as the proper media is used.
Sand is bad. That mostly applies to welded, heat treated frames such as Cannondales.
If your Trek's tubing was heat treated prior to bonding, then sand as a media is definitely out.
If the proper media such as ground walnut shells is employed, blasting is fine. There are others that are safe
as well, but I am not sure what they are.
I am not familiar with chemical stripping on bonded frames, but one could always sand the joint areas and
chemically strip the lengths of straight tuning.