How do I drain the battery before opening the device?

Hi there!

Since my ear speaker is painfully silent during calls, I thought it appropriate to open the phone with some newly bought tools from iFixit and try to clean it out before I think of repairing it. From the guides on this website, I see that it’s recommended to drain the battery to 25% and lower before you open the device, to provide some extra safety against fiery accidents.

The question is how I do this the quickest way possible? I’ve read around on the Internet that I’m supposed to raise the back screen light to the max, open up all the applications at once etc. to drain the battery, but I find this kind of solution to be pretty slow as well. Is there a better and faster way to drain the battery? What do the professionals do?

Thanks in advance! :)