6:35 minute, 26:17 minute and 44:58 minute - Manufacturing of injection moulded devices requires a certain draft angle to be used, typically in the range of 2 degrees positive inclination. This means that the ! _ExtrudeCrvTapered _Pause _Solid=_Yes command is useful there.
9:10 minute - The one way to make tiny sharp corners look as if they have a radius fillet is to actually as a radius fillet. ! _FilletEdge is your best friend in this situation. 
9:50 minute - Adding a blend surface is only justified if the geometry is complex. Since the mode is a simple box made out of flat surfaces, the better method is to stick to the flat surfaces and simply use fillets. This also helps later, when adding a shell thickness or offseting certain surfaces.
15:35 minute - Last post in the following topic:
16:44 minute - Perhaps it’s a good idea to teach people how to take advantage of the Cursor ToolTips?
18:03 minute - “PushPull” failed to combine the extended vertical fillets and flat surfaces.
25:03 minute - Instead of the method shown in the video, the better way to build those diagonal lines is to build one line from center to center between both circles, then either use offset curve (if you know the diameter of the smaller circle) or make copies using tangency snapping.
27:16 minute - Always try to use Ortho when making circles. Helps a lot with the latter design process (especially CPlanes to build curves for the Revolve of the button) and tooling for manufacturing.
30:00 minute - Teaching the users to take advantage of custom display modes with real-time shadows is essential to better examine the depth of the geometry. If you compare Rhino’s defailt Shaded mode with “Shaded 5 Black” or “Bobi X9”, you will clearly see the difference.
31:05 minute of the video - Bug report here, related to the GUI (inability to render the pop-up menu).
33:20 minute - A great opportunity to teach people how to use ! _OneView or CPlanes to make the profile of the button, then use ! _Revolve (or ! _RailRevolve for prolonged buttons).
36:35 minute - While blends are more pleasing to the eye, very tiny edges typically use ball fillets, because the manufacturing process involves very small ball tip tools that are quite expensive. To minimize the cost, tiny fillets are made with radius fillets instead of blends that require a lot more time and broken tools to carve the steel injection moulding dies. anything less than 1-1,5 mm could be radius and will not make a real difference if it’s made with blends, but the cost of manufacturing and time will be substantially smaller.
37:45 minute - Snapping to the center of a circle with fillets or blends is not recommended, because Rhino tends to snap to a bit wrong coordinates. It’s recommended to snap to the CPlane zero or a preliminary built center point, which is locked or placed in a locked layer to always stay in a fixed position.
38:16 - While building or editing curves and lines, it’s much easier to see them on display modes that have an appropriate colour. Yellow selected lines are difficult to see on a nearly white display mode.
46:47 minute - Perhaps using ! _TweenCurves is faster and easier if you want to build multiple scaled circles? However, in this design case specifically, I would use a profile curve drawn from a side view or a vertical CPlane, followed by ! _Revolve.