yeah offset would work for the grooves. remember offset works proportionately around all the faces.

I used scale because I tapered the front and back edges in a bit more then the taper on the sides so I just used individual scales on the appropriate axes.

I tend to use offset when I want to take all the faces and apply an uniform inset on all edges.

when extruding an entire surface to add thickness the z-axis is usually the one that will do that. The z-axis extrudes all face along their normals. On a cylinder this means as you extrude inward all the faces will narrow inward toward a central axis running the length of the cylinder.

This should only become an issue if you are trying to add a lot of thickness. For thin walls of something like the heat shield / radiator / heat sync it should not really be noticeable.

Don't worry about asking questions that is the point of these forums and sites. I am sure everyone here is more then happy to lend a hand. As you watch the videos if you have time send me an email if you have any suggestions on how I can improve them or if there are any bits that really confused or confounded you so I can make them better.

Cheers!