The key is you can learn to draw fast but still keep decent line quality. It doesn’t take any more time to make one clean stroke as it does to make a bunch of small scratchy ones. Drawing is about muscle memory, and as you practice and develop your skills your hand will naturally gain more control.
Spend a lot of time drawing with ball point pen. Ball point pen allows you to start really light and build up color and weight. It also never needs to be sharpened and if you make a mistake, you’re forced to learn to draw around it.
It’s not about saying “my stuff is crap” it’s about being able to look at a drawing and say “hmm, the degree of these ellipses is off” and draw it over and over again till you can look at it and say “there we go, that looks right”. If you get a pile of good sketches and can effectively copy them you’re guaranteed to learn the techniques of how they do things. There are lots of great materials out there like the Scott Robertson drawing DVD’s that are great for beginners. Even if you don’t use his style, theres tons of useful material and techniques for understanding lines and shading. Once you learn how to construct the perspective you can practice moving away from it and just sketching things freehand. Without understanding that perspective though you won’t be able to know if your freehand perspective is correct.
I STILL draw through the majority of my drawings, even if it’s just a faint contour line to know if things are lining up.
Practice drawing really large as well, drawing bigger is always better. Shrinking down a giant sketch thats OK usually makes an awesome sketch when viewed on the computer at small size (especially if you put it in a field of 50 other good sketches).
I don’t believe that you’ve spent “endless” amounts of time on trying other peoples tutorials and techniques. Try setting a goal of something like 3 11x17 sheets of drawings before bed. Then when you wake up in the morning look at them in the mirror- (which is great for pointing out bad perspective) and make little notes of where you think each one could be improved. Spend the next night drawing it over correcting that mistake. Practice throwing in hands, arrows, callouts, background boxes, shadows, etc.
I guarantee if you keep that up for a semester by the end of it you’ll really say “wow, the stuff I drew 4 months ago was terrible”. I look back on the stuff I drew all the way up till the end of my 3rd year in college and it was just awful. Every day over the summer I’d come home from work, cook dinner, and draw till I went to bed. By the time I came back to classes in the fall my professors and classmates thought I was a different person. I’m still not nearly as good as tons of people from art schools, but it was enough to land me a job - and really thats what counts. Unless you’re going to school to design cars you don’t need to worry about being amazing at flashy photoshop renderings - you just need to be able to very quickly get your point across and make it clear.
Oh yeah - and the secret to keeping a verithin pencil sharp is to both draw on very fine paper (the harsher the tooth on the paper, the faster it will wear down) and to learn to rotate the pencil while you draw, so it wears evenly on all sides.