Someone propose that I make getnewaddress and dumpprivkey that address,
he will do same at his wallet, and we exchange each other's privkey generated from above, then importprivkey.
and if I input coin to there, that become multisig, both signing need and safe.
Is this true?
No scam factor here?
That is not how multisig is done. Do not share private keys. If you give someone a private key, then they can spend the bitcoins at its address.
Multisig is done like this:
1. One person creates a transaction and signs it, and then sends the signed transaction to the other person.
2. The other person also signs the transaction, and then broadcasts it to the network.