We publish a toolkit with web interface. You can now create, sign, and broadcast multisignature transactions with Counterparty Assets and bitcoins.
It works with Mainnet and Testnet. Have fun using it as online step-by-step tool or use each step independently. Sources are available at AmiLab’s GitHub repository.
AmiLab’s tools at GitHub
The service is developed using several AmiLabs toolkits. During development for blockchain and Counterparty we made a dozen of github repositories. Almost ten of them are public and open-source under MIT license, meaning anybody can use it even in commercial projects.
Keep in mind that those toolkits are not well described or documented. However, it may be very helpful for developers. Feel free to use developer branch, because master may be not available soon.
See also the post at amilabs medium blog.