Blender Part

Fit The Outfit To The Body/Head

Pose Mode

Proportional Editing

<aside> 💡 Tip: Start by using a huge area for the proportional editing tool (Scroll Down with your mouse). Using a big area for the start allows to place the outfit on the base without distorting it too much, it is fine to fix a place and create clipping on another, go with iteration back and forth until the clipping almost disappears. When the clipping is almost gone, you can decrease the proportional editing tool area (Scroll Up with your mouse).

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Transfer Shape keys

the weightpaint transfer has to be done on the deformed mesh 50% (work for a solution to make the shapekey transfer not a 50%)

first make the outfit fit everything at 0%
second make the transfer shapekey
third make the transfer weight at 50% all body relevant body shapes

Weightpaint

Transfer Weights

Select Body + Shift Select Outfit
Go in Weight Paint mode
Go in Weights → Transfer Weights

This window pops at the bottom left of the viewport when you click on Transfer Weights

<aside> ⚠️ Warning: Mix Mode = Replace ; that means if the mesh receiving the Weights had vertex groups with the same names as the mesh sending the Weights they will be replaced!

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Adjust the weightpaint (advanced)
1. Use the smooth tool in Weight Paint mode
2. Bones animated with PhysBone might have received unwanted weightpaint

Make Blendshapes

To make the work easier, we will use the plugin Mesh Data Transfer. It will Transfer Blenshapes (the way as we did with the Transfer Weights) from the body to the outfit.