I am wanting to convert my flex duct in my crawl space to metal duct. However, the duct at Lowes seems flimsy. I also am having in the summer condensation on my ductwork. I want to eliminate this.

Can I use the expanding spray can foam sealant or rubberized undercoating like you use on a car to spray the duct before installation, then wrap it with the duct wrap insulation to maximize the insulation value of the duct and to give the duct rigidity?

One last thing, can a person buy the professional spray insulation material and spray it themselves at home in the attic etc? I have a large air compressor and several spray guns? I would like to add some insulation myself, especially in the attic.

I really appreciate it!