Design your decoy
Long experience on measuring ships deploying decoys shows that the best way to get a good decoy is to use something going out from your vessel with high RCS. It is possible to do exactly that. Using drones carrying corner reflectors.You can design these with cadRCS so you know that these make a higher RCS than your vessel. With the right number of drones carrying corner reflectors this can be brought to work especially if you have made your vessel stealth. It is also a cheap solution and you can make training with it for almost no costs as the drones and corner reflectors can be reused.