The following are my experiences, your mileage may differ:

1.  Miki4 is the worst weightmapped figure to "begin" your weightmap rigging experiences.  Every JCM, every FBM, and every PBM has to be adjusted in the clothing on Miki4.  There is no easy way to rig for Miki 4.  Work with Anastasia, V4WM first.  While not easy to rig, they ARE easier than rigging for Miki4.

2.  Nerd's videos really are helpful, but you're just going to have to get in there and play with the weight maps in order to understand what he is doing.  Paint, play, but don't save.  It's the only way to learn it.

3.  Here's a confidence builder for you.  Using any character, load the character, load and conform clothing, then raise the shoulder to an extreme level to CAUSE pokethrough. 

3.  (b) go into the Joint editor, select the shoulder, select the morph list, select ShldrUp and now push, pull, smooth that spot on the clothing causing poke through.

3.  (c) zero rotation and save your clothing to the library.  You have now permanently repaired that morph which causes the pokethrough on the clothing item you just saved.

There's a Nerd3D video for this as well.

Weight maps are much like the example in 3 above......painting, pulling, pushing, moving....until it's right.  In addition to the weight map, you have the bulge maps, if used. 

Learning how to rig with weight mapping should be a process of trial and error to see what is effective.  It's not hard, but it's no less tedious than Poser rigging has ever been.  Take your time, don't look for shortcuts, and learn what/why you're doing what you're doing.