The plastic Junker head is not too dissimilar to the metal one. I would recommend carefully removing the rivet circled in red here, which spoils the effect. If you are feeling confident with your putty skills, you could also separate the visor into two eye slits. I’m not going to for this tutorial. There is also a rivet on top of the helmet. I had a mishap with mine, so I removed it.
Add the head to the body, and fill the gap under the chin with some putty. We’re going to sculpt a mask over it, so it doesn’t need to be perfect.