So seemingly out of nowhere the blob brush tool stopped working for me. Every time I try to set the stroke size or the fill and outline colors the settings auto reset with the outline color becoming the fill color and the stroke size reverting to 1. New Art Has Basic Appearance is unchecked and I have tried reinstalling Illustrator and resetting the preferences.
The Blob Brush always draws with the stroke color. If no stroke color is assigned, it will shift the fill color to the stroke. If a fill and stroke color are assigned, the fill color will be eliminated. When you deselect the Blob Brush, the area that was covered with the brush stroke becomes a unified fill. If you want a stroke around the generated shape, you can add it at this point; you cannot apply it as you draw with the Blob Brush.
To adjust the size of the brush, use the left and right square brackets, [ to make the brush smaller or ] to make it bigger. The displayed stroke size will always be 1 pt.—do not use stroke size to set the brush. You can also double-click on the Blob Brush Tool in the Tools panel to set the size and other aspects of the tool.
I know how to resize the brush I wasn't using the stroke size to adjust that, I was using it to adjust the outline width - which was auto resetting and not maintaining itself. But yea, maybe I didn't make the issue clear in the video but previously I was able to use the blob brush to draw shapes with an outline and then I was able to continue drawing and adding to the shape after reselecting it. The issue here is that when I deselect it and then reselect it, if there is an outline color, the brush switches that and makes it so I can't continue to edit or add onto what I was drawing before.
The blob brush will always use the stroke color as its fill. That's the way it works. It doesn't understand strokes.
I'm using CC 2021. THIS IS A BUG!!! When I use the blob brush at 75% opacity and I color a portion of the artwork, then color a non-adjacent detail using the SAME COLOR AND OPACITY, when I attempt to add to the original area using the ORIGINAL COLOR AND OPACITY, Ai automatically converts the opacity of the new area to 100% opacity and treats it like a separate object. I have tried setting the opacity before using the BB, it reverts to 100% opacity. I tried setting both the stroke and fill to the desired color at 75% opacity, Ai converts any new BB applications to 100% opacity. If I go in and select the newly applied area, then change the opacity to 75%, Ai will change the opacity of the new selection to 75% BUT, instead of an undetectable join, there is a darker area where the two applications overlap. When I delete the non-adjacent details, further applications using the BB works as expected - the new area is added to the existing area at 75% opacity and without an overlap.