Step #1: Plan out your Line Variation and Brushes before you start in Adobe Illustrator. If you didn't, use the simple method of finding the floating ends of the line. This will signal the value change ended while you were drawing. This will be a tapered end of the line.
Step #2: Match the Brushes to the Line Variation. If you planned out your lines in your own drawing, this step is much easier. Select the Brushes and Line Weight. The easiest method is to find the ends and visually find the other end to see if it will be floating or hitting another line. If it hits another line that signals a darker value to the end should reflect the change in value. (Thicker End).
Step #3: Moving towards Editing your Brushes. Duplicate Live Brush Layer before Expanding. Expand All. Object - Expand Appearance + Expand. You really only need to Expand the Strokes. Path Simplify Option: Once the Brushes have been Expanded hit the selection with a Simplify Path ( Object - Path - Simplify) to clean up extra Anchor Points.
Step #4: Editing using Shape Builder. Select All. Select your Shape Builder Tool. Hold down Alt/Option on your Keyboard to Delete. Hit all of the overlapping lines to clean up any of the extra lines. You can Turn Off the Highlighting feature in Shape Builder. If you have busy areas, I will recommend zooming in.