decompile the trunks model, that will give you all of the animations you need, and the qc file you want,
import the skeleton from the trunks model, (unless you have already done this part) and assign the model to it, now export it back over the reference smd file, (probabaly called trunks.smd) and then hit compile qc file within milkshape, locate the qc file created when you decompiled the trunks and select it,
if you did everything right it will have compiled your model into a MDL, if it didnt, you di something wrong
(i know i skipped a few steps, but thats the jist of it)