I found an old bottle jack at a thrift store for a few bucks, at a glance, it was non-functional and would just bounce up and down. In the current state, it's unusable and potentially dangerous.

I hate seeing old tools get thrown out when they can be easily fixed and I'm a firm believer in 'fix, not replace'

Supplies

A busted old bottle jack
Transmission Oil (or jack oil if you have it)
Kerosean
Wire brush
Paint
Paint stripper
Brake Cleaner or other degreaser

Step 1: Drain & Flush

The first step is to remove the little rubber plug and drain the old oil out. This jack was missing a lot of oil and what was in it was pretty dirty.

I like to give the jack a flush of kerosene at this point to purge any remaining oil from the jack.

Step 2: Disassemble & Clean

I then completely disassembled the rest of the jack and gave everything a good wash with kerosene. While it's not necessary I stripped the old paint off and gave everything a final clean with some brake cleaner.

Step 3: Prep & Paint

I then used some masking tape to cover the parts of the jack that I didn't want to paint. Now give everything a couple of coats of spray paint and once it's dry remove the masking tape.

I let everything cure for a few days so it can harden a bit more.

Step 4: Reassemble & Prime

You can now reassemble the jack, use a small amount of oil on all the seals and then tighten everything down.

Now for the most important part use a syringe to fill the jack with oil. You need to prime the jack by pumping it a few times and then topping off the oil again. Once you have pumped it a few times back off the release valve and while it's open pump it a few more times. The jack should be fully primed now, give it a final top off of oil and insert the rubber plug.

Note: If you have jack oil use that, otherwise transmission oil will work fine.

Step 5: Clean & Test

Now give the jack a wipe down to remove any oil you spilt and you are ready to test the jack. When using a jack make sure to operate it safely, never go under a load that is held up solely by a jack, be sure to use axle stands or some other kind of block.

You can now see the jack operates correctly. I now have a dirt cheap Bottle Jack and saved some waste from the landfill.