Tin snips sharpening

[valdim]

Hi guys, I bought these German snips from a local market and thought I would just have to remove the rust and oil them...
Now , it turned out I have to sharpen them, too...
Never sharpened such tool. I guess principles are similar to sharpening scissors. Anyhow , I took some pics and a video , so that you can tell me how to approach the sharpening in this particular case. As far as I notice, it is the worst on the last 2 cm from the tip - the snips just bite the tin, don't cut it.
Thanks for any advice.

 

[coxhaus]

If I had to guess, take them apart and sharpen like scissors. I would use my Worksharp. If not follow the lines with a small stone.