If you are using an OEM filter kit, then you shouldn't need any sealant. As for the ATF gushing out, one how much ATF did you add and did you empty the torque converter. When I changed the ATF in my car, I made the mistake of trying to add the "fill quantity" without first starting the car, to allow it to work into the converter. Since I didn't do that first, the ATF I was adding forced it's way past the gasket. Once I started the engine and went through the gears, the leaking stopped and I was then able to add the rest of the ATF.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member