The best and easy way:

• select the cloth part (mostly hip if it's a skirt);

• add a magnet, as FrankT said, from the menu -> Object -> Create Magnet;

• select magnet, mouse right click -> Element Style -> Outline (so you can see thru it);

• select Mag Zone and preferably lower the zScale to 50% or less, xScale to 150-200% and leave yScale as is (for the moment);

• now select the magnet and move the yTran dial to +/- 0.500, you will see the mesh moving;

• if the "bulge" isn't in the right position, increase or decrease the yTran and zTran in the Mag Zone;

• if the magnect affects almost or the whole skirt, you can lower the yScale to 70-50%;

• adjust as needed for little tweaking and add other magnets as needed;

• repeat the operations with the back of the skirt and for the right and left parts if necessary.

• if the skirt is subdivided in more parts, repeat the operations, add other magnets and copy and paste the parameters (Mag Zone and Mag) from Hip to the other parts;

• at the end, when you have a good result, select every single part and go to menu -> Object -> Spawn Morph Target, give the new morph a name, delete the magnets and use the new morph added.

• set all the new morphs in the cloth (only those morps!) to 1.000, select the Body, go to menu -> Figure -> Create Full Body Morph... give a name to the full body morph (the same of the single part), set to 0.000 the new morphs in the single body parts and now you can use the morph in the Body.