I'll just mention what CAT wanted on their exhaust "slip joints".

Cat sells some exhaust sealant, in a small pint sized paint can-style of container ( Edit: mix it with screwdriver, before applying), that they only wanted us to "coat" the MALE portions of any exhaust sections(before insertion) = They didn't want any sealant globs, inside exhaust manifolds, after reassembly. {Don't add to the Female areas}

After I got the complete exhaust manifold mounted to engine, and torqued; I used some surgical gloves and molded the excess sealant around external male/female joint, made it look like "bathroom tub chalk joint" .

Don't know if Cummins procedure was similar or not.