We may be a bit old fashioned in our approach to keep chains on our tandem + one single bike clean.
Remove chain and soak in kerosene or diesel. Scrub with stiff brush and wipe down with rag, then let dry.
We use a one burner electric stove (outside) and put metal can with a couple bars of canning wax to heat and melt. Drop/lower dry chain carefully into melted wax for several minutes. Shut off electric burner and remove chain carefully with long handled pliers and let dry,
After chain cools, wipe it with rag a couple times and re-install chain.
For first couple rides you may notice some black flakes on chainstay (that's dried wax).
You can grab chain bare handed and not get dirty like with oil.
The liquified wax has penetrated where lubrication is needed: around the pins.
Chain that is waxed does not attract dirt like wet lubes/oil.
Do not toss out the can with the re-hardened wax . . . it's re-usable for several more times.
Living in a dry climate (Arizona) we can easily go a couple thousand miles before we hear a slight chain squeak . . . then it's time to repeat the process.
Been using this method over 30 years and works for us.
Pedal on TWOgether!
Rudy and Kay/zonatandem