A few years ago i ordered Castrol Syntrans for my Golf. I didn't realise what was sent was Syntrax, a diff oil. I filled it, went to drive the car and it would only select a gear when stationary. Couldn't shift from first to second when rolling.
Really odd, but it seemed to stop the synchros...
There's an episode of The New Detectives on Youtube where they discuss a case of a man who disposed of his wife by means of a chainsaw and woodchipper, firing the waste into a river.
He got caught, so probably not a great solution.
Looks like an AMP Junior Power Timer.
https://www.3waycomponents.co.uk/product/282191-1-amp-tyco-3-way-junior-power-timer-with-terminals-boot-and-cable-seals/
I have 3 and use them all the time. If i can use one instead of a hydraulic jack i will, quick and easy.
The Selson ones are the best i've used but they're £400+ each.
But if maximum lifting height is a concern i'd get a high lift long chassis jack instead.
I've tried a few different things, but that Tap Plus is without a doubt the best i've used. I mostly power tap in the mill or lathe and that stuff makes a significant difference. I was very skeptical of it until i tried it, but now i'm sold on it completely.
If you want a small pot of it to try...
Get decent sealed LED units and wire them up properly insulated with proper junction boxes.
These have been on for 4 years, trailer lives outside, everything works perfectly.