There was mention in a paint thread over the last few months of a product that is a two part poly clear, but it comes in a rattle can. Apparently very hard. Available at US auto outlets. Not that it will be all that durable over raw metal, but it might be better than the option.
This is becoming one of those questions that is asked frequently, so far I have not heard of a really good answer, that either says what works for pros, or what would work for the rest of us. Sounds like a bit of a looser, where low expectations might be the key. I have successfully polished crazy glue, and it gives some protection, so I would probably try that, hard shinny, and instant.