Let the sealant set thoroughly according to the instructions on whichever kind you are using.

I'm not going to let a big split develop in the casing again since water getting inside the mechanism causes so many problems.

I'm not sure how well silicone sealant will last but if it isn't hard wearing enough I'll try Sugru or something else next time as soon as that area looks like becoming a problem. Ideas or suggestions for alternative waterproofing materials? please comment!