Be careful about spraying silicone on thread BEFORE it goes through the tension. Over time the thread can carry the silicone onto the tension disks, where it can build up and begin reducing tension. It's better to apply after it comes out of the tension. There are some after-market products that are tiny sponges which stick to the machine in the thread path. You apply the silicone to the sponge. We've never found it necessary to lubricate the thread though. Using a topstitch size 14 needle is a big help.

As for taking to the roof, remember one has to suffer for one's art!