I managed to transfer some of my delegated GRT to L2 via the network explorer from my old validators, but what is the easiest way to delegate to it if you have undelegated GRT in wallet?

The Arbritum bridge only asks me to put on 3rd party spending cap when I try to transfer the GRT but transfering ETH was easy and it didn’t ask for spending cap. I don’t understand why I can’t seem to transfer GRT via the same bridge, only set a spending cap but the transaction to L2 will not proceed.