I know many logger types around here who do not know how to turn on a computer!
So by placing ads on the internet, you could be missing quite a few folks who might want to buy that equipment.
Of course place your ads on the internet, but also get the word out to the non-computer types the old fashioned way...
That is have your father-in-law call everyone he knows in that line of work. Or mail them printed pictures of the equipment.
Here in Oregon we have a loggers association called "Associated Oregon Loggers" and their web site has a section for equipment for sale (nothing listed there probably because many loggers do not use computers :msp_confused: ).
Associated Oregon Loggers: Home
Perhaps your area has similar associations? And maybe you could pay to place an ad or flyer in a regular mailing they send out to their members?
Or if there is a logging supply store in your area, perhaps you could post a flyer?
A lot of this stuff is word of mouth. Get the word out to a few in that line of work, then they will tell others.
As to the mills around here, they have recently torn out all the old equipment and installed new computerized equipment. So I don't think they would be interested in any older equipment?
Ask your father-in-law if he subscribed to any magazines specific to mills or belonged to any mill associations. Or received regular mailings from any "group". If he received those mailings, then other mills would have too. And that would be where I would try to place an ad or get a flyer inserted in a mailing.