Vulnerability hunting

This is a very hard way. you need to do reverse engineering of all Motorola boot loaders

For more information see here:

Security in Motorola Android Phones family

Boot chain

Disassembling

Here you can find useful things for the IDA Pro for droid reverse engineering: http://gitorious.org/droid/ida

Here you can find latest IDA databases of these boot loaders http://gitorious.org/droid/reversed