How do you keep your mash warm?

[foothillbilly]

I'm new and learning and want to say thanks. I do try to search as much as I can with the search feature but have not seen anything on this topic. I'm using a 5 gallon water tank that you find in many business'. You know the blue ones. I was thinking of sitting the full bottle into a storage tote and fill it up with warm water? Around 90 degrees.

Thanks in advance
Hillbilly