The Max Drive Pro method is by the most easiest and faster solution for booting unsigned code (bios, emulators, etc) on the Nintendo GameCube and the only disadvantage to this solution is you're still going to have to swap discs, but only once (or more depending on the BIOS you use.)
REQUIRED
Max Drive Pro
Any SoftMod BIOS
You can purchase either the Max Drive Pro or the Action Replay Evo Edition directly from http://www.codejunkies.com. You will notice that both of these items are “usually” on backorder. Just order the unit and it will be shipped to you shortly as these items “are always listed on backorder”. There are two versions of the Evo pack in production so make sure the one you purchase includes the "Max Drive Pro" and not the normal "Max Drive".
The Max Drive Pro is a hardware unit that can interface with your computer using USB and plugs directly into the GameCube using a spare memory card port. It also consists of the DOL (GameCube Executable) loading DVD which you use to boot your DOL's with.
Simply copy over all of the BIOS you wish to use (GCOS, NinjaShell, GCOM, Ananconda, etc) to the Max Drive Pro using your computer, put the Max Drive Pro into the GameCube, boot the included DOL Loading DVD and select which BIOS to load. Once the BIOS is loaded you can do whatever you like with it - boot backups, backup games, browse DVD, etc. Please refer to the BIOS section and/or it's included documentation to see how to work the BIOS you've chosen to use.