Is multisignature usable, if so what is the business process Im interested in the application of multisignature, for example in a business context.

I see clear and simple instructions on creating a multisig address, and sending to the address seems fairly obvious.  However the process to send from multisig, seems sparsely documented and often many versions old.

Is it practical to use multisig on a Core wallet?

If so, in simple two of two scenario, what is the process of generating a transaction?

Can a third party holding neither of the private keys, propose a transaction for the two signers?

Do they all need to use the same terminal?

How does a signer know a transaction is waiting?

If there are multiple transactions proposed, how would a signer sign some but not others?

Thanks.
Is it practical to use multisig on a Core wallet?


yes, but for sure it depends on your level of comfort. It's not (yet) plug'nplay :-) See also the example from Gavin at the end.


  If so, in simple two of two scenario, what is the process of
  generating a transaction?


see example.


  Can a third party holding neither of the private keys, propose a
  transaction for the two signers?


yes, a third party can create the transaction, and post it to the network (he would need to have the bitcoin addresses of the other  participants, to create the redeem script).


  Do they all need to use the same terminal?


no, not at all. I have done creation of the funding tx on my online system, and signing of the spending tx on an offline system (cold storage). 


  How does a signer know a transaction is waiting?
  there is no protocol inside bitcoin for "notification". When you prepare a multisig, you need to have a different communication channel than the bitcoin network, to inform on necessary signing. 


Example:
https://gist.githubusercontent.com/gavinandresen/3966071/raw/1f6cfa4208bc82ee5039876b4f065a705ce64df7/TwoOfThree.sh

btw: next to the examples to bitcoin.org, Andreas book "Mastering Bitcoins" (2nd edition) has many references to multisig, and it's wortwhile to read. It can even be found online.