Oil leaking from oil temp sensor

[Mike T]

I installed a new Oil Temp Sensor and crush washer on my R1100RS. Given the location of the sensor I had a hard time getting a 19mm wrench in there to tighten it up. I noticed yesterday that a small amount of oil was leaking from that area. Are there any tricks on how to tighten this sensor? I'm going to try and buy a thinner 19mm wrench today to see if that allows me a better angle to tighten it up. Should I use any gasket sealer on the threads?