There is no SCRIPT in BitShares. Every functionality has it's own *operation*. A simple transfer operation looks like this:
[0,
{'amount': {'amount': 100000, 'asset_id': '1.3.0'},
'extensions': [],
'fee': {'amount': 264174, 'asset_id': '1.3.0'},
'from': '1.2.282',
'to': '1.2.880'}]
Multisig is done on a *per-account* basis and not on a *per-address* basis because BitSHares doesn't use addresses. It only knows accounts.
Lots of documentation can be found here: docs.bitshares.eu