I went with the Noico route and i bought a 1 inch roller at same time from amazon. I just put one layer on roof of my 06 Taco AC, took the tinny sound from rain out, and im a happy camper with a better sounding stereo. Going to do doors and back of truck next with a bit more deadening for next...
take the shroom and put on white paper, leave over night if its a blueish purple color your in happy land. Lots of vids on Utube on this type of mushroom