I have been reading the different methods that everyone has been using to weather wood.

I have been using one of two methods for 40 or more years.

The first is to take a bottle of white vinegar and some fine steel wool.  Get a large jar and  insert the steel wool.

I just read your information on gluing sheet metal to cardstock.  After years of building custom models for customers, I have tried about every type of glue you can think of. From white glues, to a variety of super glues.  Contact cement, works  well, but your method of the double sided tape is probably the best yet.