var tx = new Bitcoin.Transaction();
tx.addInput('4f6e1ea426c473a19498af663cae314669451678cabbb633e87b401087c7064c', 0);
tx.addOutput('mhaTL1onPYtM3xpkXWqaA1DnNNgHYhEsDP', Wallet.toSatoshi('0.499'));

// var signatures = privKeys.map(function(privKey) {
privKeys = [Bitcoin.ECKey.fromWIF("91uWV4hLdpKHNFcBaD1sT5jfEFP5nujwimfARKbvkZ6L3Hmo7t6"),Bitcoin.ECKey.fromWIF("92H9tQ9oUxgGPxXVzkPhiQRVZFc2DGBbbaYx9HtSiPAnALvHvH1")];

var signatures = privKeys.map(function(privKey) {
		return tx.signInput(0, redeemScript, privKey)
})

var redeemScriptSig = Bitcoin.scripts.multisigInput(signatures)
var scriptSig = Bitcoin.scripts.scriptHashInput(redeemScriptSig, redeemScript)
tx.setInputScript(0, scriptSig)

console.log(tx.toHex());

// This basically signs something with both private keys at once.. but how can I sign with one private key, store the output, then sign with another private key.. before finally then pushing the tx ?