Yes, it was done using a mouse. Some people actually tried to tell me that I didn't use a mouse but it wasn't their hand that was sore at the end of the day.
The sketch itself was done traditionally and then I utilised Photoshop brushes to create the piece.
Honestly, I do not recommend using a mouse at all to do digital art, it is extremely tedious because you have to zoom in to every feature to add the most basic details. The end results look choppy as well and you have to keep blurring things out and rely on gradient features for lighting (highlights and shadows). Along with this, excessively using the mouse for digital art can lead to problems in the future such as RSI.
The benefits? I wasn't sure whether to buy a graphics tablet and try digital art out like most artists so this was a great opportunity to test out Photoshop brushes I didn't really look at before (please keep in mind that I was already familiar with Photoshop for a good couple of years so I didn't just magically gain photo-shopping skills overnight). It also gave me a chance to watch tutorials on Youtube by other mouse drawing artists and learn about features I didn't even know existed. Overall, it was one of the best experiences I had drawing and I was pleased with the end result; so, from the day I uploaded the piece, I started to save up for my new graphics tablet.