How to put two fonts into one?

[ddyourself]

I searched this forum and somebody had uploaded a package with nimbus-uming-14 fonts installed.  I truly love the nimbus font, but the size of this package is a little bit larger, is there any way to resize this package to 12pt.

Another question is how to combine two fonts into one? I have a firefly package which looks very good for Chinese characters, but not so good for English. I was wondering is there any way to combine it with nimbus.

Thanks,