Meh, been meaning to do this, anyway a some what quick tutorial on how to add clothes to any model. I know I wasn't using a base when I did this, but the techinque is still the same none the less.
TIPS:
To open up your editing menu to go V- A in the model view/editing thing
Hold SHIFT to select vertices
CTRL to deselect Vertices
Click DELETE on keyboard to delete...duh. :P
Remove bones, joints and physics only the parts that don't apply to your clothes. EX: Pants I wouldn't need the upper body bone and up as well as the arms
To apply the part to the model, drag the file into PMD Editor. A box with open, in the first part, click the second option, leave the rest along and click yes.
When applying your part, you might need to edit some. Anytime your editing a certain part, you might need to select the bones, physics an joints to the area your working in. If you don't, your model might spazz out like hella crazy. It depends on the part. :P
REMEMBER- Always save and test your model in MMD. I like to name each edit I'm working with even if minor so I know what I did wrong and can always go back to the previous edit. :3
LASTLY- Deviant Art is your friend. Parts and tutorials. I suggest going their if you have questions or looking for certain things. :3