First, have you bootmii installed on the bricked console? I think no :)
The thing you have to do first is to find a "donor" console with the same version of boot1 and bootmii installed and do a backup.
Once you have this backup, with and hex editor strip out the last 1024 bytes (containg bootmii infos and keys) and then you can flash it directly "as is" on the nand with an infectus2. This is the hard part of the work, the installation work requires soldering skills and is not so simple. In addition infectus2 seems very unstable on read and write the nand.
Obviously the donor backup will not unbrick your wii but will let you to start bootmii !! Once you get bootmii running on the bricked console you can do a bakcup and extract the keys needed to run betwiin.
Read my post, where I unbrick a console with bootmii installed : [
forum.wiibrew.org]