If you are using a newer version of Photoshop (I was using Photoshop CC 2018), you might have difficuly finding the Photoshop brushes the guide makes allusion to, as they have been removed.

Thankfully, though it took some trial and error, I found a way to re-enable them.

STEP 1: Go to the Brush Preset Manager. To do so, you must have the brush tool selected (press B), click on the downward arrow next to your current brush shape in the tool bar on the top left of the screen.

STEP 2: Once you are in that menu, click on the gear icon, and then on "Preset Manager" within the dropdown menu.(This will all be in the images at the end of the post).

STEP 3: In the Preset manager, after making sure your preset type is on "Brushes", click on the gear icon and, at the bottom of the dropdown menu, on "Legacy Brushes". A popup warning should appear. Press "OK".

STEP 4: And you're done! Even without the icons, you can find the brushes in the normal brush select menu (toolbar top left of the screen when the brushes are selected), using their names to find them. For the purposes of this tutorial you only need "Round Point Stiff" and "Round Blunt Medium Stiff" under "Default Brushes" under the new "Legacy Brushes" heading.