Sound deadener goes on the inside of your tub. Not the outside. To many painfully obvious problems to even bother mentioning. The least of which is getting to the entire bottom of the tub with everything that is in the way. And clean up - so it would even stick. Ridiculous idea. Put it on the inside. Like every single guy or company that's ever laid sound deadener.
One note on the Home Depot product. It's very very thin. And the asphalt is runny. The rolls at my local HD actually had runny fluid inside the package. It also off gasses some chemicals you don't want to be inhaling. It's asphalt based. It's meant to melt into your roof so that it fills any holes or cracks. Like the asphalt or tar that they roof houses with.
That's not to say it won't work. Tons of guys have used it. But if you look at it in the store compared to actual sound deadener there is no comparison. And the Noico is very cheap. This is a serious case of buy once cry once. As once you put it down. It's not coming back up. And if it stinks or runs. You've got it on the inside of your vehicle for life.
I think Chris spent less than a hundred bucks doing his TJ in Noico. And Noico is leaps and bounds a better product than the HD stuff. I've done deep research on all the options out there. And I wouldn't use the HD stuff. When a hundred bucks or less will get you a much higher quality product.