Happijac lubrication

Excellent post. I bought a secondhand truck camper with these jacks. The previous owner had printed this post and put it with the documentation. I just spent a full day cleaning the dirty grease out of one. A previous owner had put grease fittings on it. Seems like a good idea but grease gathers dirt and sand. It is like trying to clean a square closed breach cannon. No fun. Since the Happijac doesn’t have any scrapers the dirt gets pulled up between the square tubes and jams them up. The Happijac instructions say to use car wax. I suspect any dry lube would be ok. If you use grease be sure to clean the inner tube before retracting.
I guess another option would be to put fittings near the top on all 4 sides and force enough grease through to force out the grime.