I use an old Scottoiler vacuum actuated auto-oiler system. It works good, but the electronic version with a pump would be better as the oil flow rate would be more controllable regardless of the temperature. As the temperature effects the oil (I use Automatic Transmission Fluid) thickness which effects how much oil is delivered to the rear sprocket. I usually leave it at a mid setting, around 2 drops per minute, and don't worry about it unless it's really cold, then I'll readjust it to increase the oil flow or it's hot then I'll readjust it again to decrease the oil flow amounts, trying to keep it at the 2 drops per minute. It's worked good for me over the years as now I'm changing the sprockets and chain on my bike after 62,185 miles and 59 months have passed since last service. I just checked
my mileage tracker page to make sure that was correct. I installed this D.I.D. X-ring chain and sprockets 3/17/18 at 68,356 miles and I'm now at 130,541 miles. Your mileage may vary...