# Download .deb to some folder

dpkg -x package.deb package/
dpkg -e package.deb package/DEBIAN

# Inside /DEBIAN - config for package and installation scripts
# Inside / - Data files (like root fs, “/”)

# When you edit/replace files, pack it:
dpkg-deb -b -Z xz -z 6 package package-new.deb

# -b = --build (read man dpkg-deb)
# -Z = Compression method, GZip, LZMA, XZ
# -z = Compression (0-6 for xz and lzma, 0-9 for others)
# default is: gzip/9

# Thats all!