Snapped sediment housing, how to make easier to tighten?

Every time I change my sediment and carbon filters using that special tool to undo them it literally requires all my strength just to loosen them because they are murder tight. I have to do them up tight though otherwise they leak while filling the tank up. Today I actually snapped the plastic housing tightening it after it was leaking.

What can I use to make it easier, will PTFE tape help? Maybe it would allow me to not do it up not so tight and not get leaks. Or can I use a bit of grease on the thread? What grease/ would I use?

I hand tighten them, never had the tool, and mine have never leaked. 

Possibly try a little bit of Vasaline on the threads and o rings. When my kit was new I had difficulty getting a full seal on some of the housings. The Vasaline seemed to help. After a while they settled. I don't know whether the o rings expand a little after a while. Obviously, if you try this, you will need to make sure that you don't contaminate the inside of the housings.