1925 Roadster door problrm

[25 TA]

I have a 1925 roadster truck and need some help with door. Only one door on passenger side (left hand drive), it is getting hard to open and close. What should I use to lubricate latch handle etc.
I am new to this, but will attach a picture when I get the hang of how to post pictures. We have had the 25 restored and running since 1964

Thanks

25 TA
New Mexico