Its always tools not rules. You do what appeals to you and your decisions can be guided by what Stan is teaching us.

Hey, @Ralph! For me, a warmup is any exercise that gets us started, physically and mentally. Personally, I like simple lines and circles because they’re quick and don’t demand much mental effort, but feel effective enough to get my hand and arm ready, and they also put me into the “I’m-gonna-draw” mindset. But the possibilities for warmups are various. Some artists like to use gesture itself as a warmup for a longer drawing or painting. And, in one of Proko’s livestreams, I’ve seen @Sinix warm up on a Cintiq by drawing and undoing just a simple spiral several times. For a gesture assignment, I think a good warmup could be to draw C-S-I lines using shoulder movements and an overhand grip (as shown by Stan in this video: How to Hold and Control Your Pencil). But this is just a suggestion, of course. Ultimately, I’d say it’s up to each artist to decide what warmup will work best for them each time. Hope this answers your questions!

sort of looks like what he was saying, although the shape of the flipper does seem to be flattened a little bit. There is a pretty sharp downturn to the body at the bottom of the flipper.

When the pencil is sharp it will produce a clean line. you can thicken the line when you hold the pencil in a different angle. Softer pencils wil produce darker lines. You also can sharpen thicker pencils like the ones they use for woodwork in an flat angle, so you can produce calligraphic lines. Whit charcoal pencils maybe its easier to make those tapered clean lines Tim Gula explain this in his video https://youtu.be/ZRnQcwKU9DE , I hope this helps. You also can sharpen the pencil more whit sandpaper. Those charcoal pencils work great on newspaper, Stan use it and explain it in his figure drawing course. I think how more you practice you produce cleaner lines and less messy lines.