Lionel Sunoco 2555 Recommendations

Go to Target or Walmart and get a cheap powder/blush brush - the fatter and looser the better. use that to clean off the dust and just hit it with the clear coat. 

Why not leave it alone? Just about any clear coat will change the look of the rust and patina. People put a lot of effort into trying to add weathering so it looks like rust. You have the real thing.

Pete

I'd skip the clear coat too.
Just dusting with a soft brush or a low pressure blower (outside).

I agree with Pete, spraying it with anything is going to change the look.  If you look at any painted object, that has a rust spot, the rust does not have the same sheen as the paint.  Unless your train room it extremely humid, this car is not going to weather more than it has.  Cool find, I had one of those when I was a kid.  Unfortunately it didn't survive.

Dust it, clean it, no clear coat. It will change it's appearance forever. Want a nicer one? Just keep looking.

Thank you everyone for the replies. I'm definitely going to leave it alone and enjoy the rust as is. My basement is very dry so it should maintain its current look. Glad I asked you guys!!