Hello,
the more "Debian way" (that means using very stable and *too* much tested packages) would be to use "initramfs-tools".
I actually avoid the most that I can to use packages not coming from main / contrib / non-free. You frequently end with problems at the end because of the libraries needed in a newer version.
 I had my ramdisk image for my custom kernel done with update-initramfs.

1. Change directory to "/boot"
2. update-initramfs -c -k 2.6.35-default1 (or whatever you called it)
3. "update-grub"

initramfs-tools were already there on my today installed Debian.Otherwise, simply "apt-get install" it.
 You said to delete the older/official kernel, at least its entries in the grub configuration file. I always keep the newer official kernel from Debian. Just in case I missed a checkbox before compiling my custom kernel.
Note that you can also use "make xconfig" to get a GUI. (You probably need libqt4-dev for that)