I am setting up my system. The features of it are:GPT partition table (not sure how important this is)Triple boot - Gentoo, Debian and Mint.Custom kernel (kernel git repo) shared amounst distros.Now I am wanting to write my own lines for grub and not have the distros place their own lines in grub. I also don't really want one distro to have the role of creating the grub.conf file.As everybody is advocating the scripts, there is no one mentioning about hand crafting one. I am fairly sure editing it by hand is safe, so long as I make sure no script touches it.Another solution that I might be forced into is to configure every distro the same way (no kernels in menu, keep the custom config synced between distros), or just use one distro to manage the boot.How should I implement this? 
How to manually manage grub.cfg for Grub2?
linux;boot;grub2
If you install it on your own (see here and, for example, here), no distribution's scripts will mess with it.On the other hand, I found it convenient to let Debian manage my grub.cfg and add other OSes (if they're not found by os-prober) to /etc/grub.d/'s custom file.