The Cressi Open Cell SMB is the ideal deco buoy as it has an open end (to inflate with your octopus) and plastic oral inflator! It can be attached to a simple finger spool and deployed from below the surface or you can simply fill it at the surface to use as a signalling device.
The reflective strip at the top of the SMB is great for identification from a bit furthe away.
The SMB has a quick release dump (overpressure valve) for easy deflation and protection against over-inflation while letting the SMB up from depth. It will simply dump any excess air or expanding air out through the dump valve. The SMB attached bungee is easy to keep the SMB rolled up and stored away.