One thing I would recommend is to REALLY focus on those mannequin skills. Every artist does mannequins a little differently (some artists have more than one mannequin they use) so don't get hung up on any one system, just pick something simple to start with (Proko's robo-bean + cylinder limbs is a great start) and carefully invent poses, focusing on rock solid clean lines and perspective (sloppy drawing will really hold your mannequins back). Over time it becomes easier to visualize things, and you'll learn lots of bone-stock generic poses that work well which you can modify (the "Masters of Anatomy" books are pretty good references for go-to poses, but make sure you're constructing a mannequin instead of just copying his roughs). Secondly, to echo nnnnnnnadie's comment - get into those poses. When you imagine one, if you get into the pose, you'll quickly realize if it's awkward or impossible. Once you can find a pose that actually feels natural you can snap a photo and draw a mannequin. Eventually you'll want to work from gesture > mannequin > drawing, or even straight to a pose Kim Jung Gi or Stan Lee style. If you struggle with getting your mannequins in perspective, just work on simple solids like cubes and cylinders until you're fairly comfortable. Also... if you get stuck, fire up Daz or Magic Poser or something and just pose away. It's best for learning if you can work out the mannequin yourself, but if something keeps coming out wonky - no rules, only tools. Knock it out and try to get it from imagination next time.

I used Sketchbook for a while (iPad), but it just never ‘clicked.’ Nothing was bad really, the brushes just never quite worked with what I was trying to do. I was really just sketching though, didn’t get far trying painting. Then I found Infinite Painter and that really works well. I just recently bought the full version as the value is definitely there for me (I particularly liked that they had a ‘Proko Brush’ which did a reasonable job replicating Stan’s soft lead with overhand grip, then sealed the deal finding the Wet Marker brush which is great to paint with). Haven’t tried Procreate, paying up front without trying it didn’t interest me and I prefer supporting a diversity of tools rather than just going with the most popular one blindly. I also use Krita, which has come a long way and is incredible as a free product. It’s a pity guides and demos on the net are almost universally Photoshop, thank goodness Marco Bucci’s recent course here also covers Krita :)

I tried treating the top and bottom "meat spear" like they were in space, being lit from a point that acted like a spot light (lit from bottom for the top one, and vice versa for the bottom one). I did have some issues with the middle "meat spear" as I tried to have it lit "point-wise" or perpendicular to its length. Any advice for that would be most appreciated.

I was rewatching the video and decided to try it out. Drew a reference (sorta bulging crescent shape) below. Used a combination of random mechanical pencils lying around (not artist mechanical pencils) for the outline, and a Prismacolor 6B pencil for the shading (as well as a tiny bit of erasing, using a Tombow mechanical eraser and a gum eraser I ripped a chunk off of).

Hi Guys, Gestural quick sketches attached. Any help appreciated. Thanks.