Has your new kernel passed the first two phases of testing? Now, you can start to experiment. That is, to do stupid things that nobody sane will do during the normal work, so no one knows that they can crash the kernel. What exactly should be done? Well, if there had been a ''standard'' procedure, it would have certainly been included in some test suite.
The third phase can be started, for example, from unplugging and replugging USB devices. While in theory the replugging of a USB device should not change anything, at least from the user's point of view, doing it many times in a row may cause the kernel to crash if there is a bug in the USB subsystem (this may only cause the problem to appear provided that no one has ever tried this on a similarly configured system). Note, however, that this is also stressful to your hardware, so such experiments should better be carried out on add-on cards rather than on the USB ports attached directly to your computer's mainboard.
Next, you can write a script that will read the contents of files from the
/proc directory in a loop or some such. In short, in the third phase
you should do things that are never done by normal users (or that are done
very rarely: why would anyone mount and unmount certain filesystem in an
infinite loop? :)).