How do you modify and rebuild a package?

[Russell Sears]

I'm trying to do the equivalent of debian's:

apt-get source foo                # download source code
cd foo
<muck with source code>
fakeroot debian/rules binary      # build new package

using MokoMakefile.

(I couldn't get the official directions on the wiki to work, but am 
willing to get them to work if I have to...)

The closest I've been able to do is:

make rebuild-package-foo   # download source, build package
<find + edit source>
make rebuild-package-foo   # blows away local modifications
<copy ipk to phone>
opkg install foo.ipk       # fails on md5sum errors

How should I be patching + building packages?

Thanks!

-Rusty