That putty is butyl rubber.
On items that are easily removable, such as marker lights, I remove them and clean all the rubber off using rubbing alcohol, then replace using new butyl rubber.
On items that are not easily removable, such as roof vents, I clean off all the Dicor, leaving the butyl rubber under the flange, and then seal using Eternabond. A good wide roll of Eternabond will allow you to butt the edge of the tape up against the side of the vent and still extend out beyond the edge of the flange, creating a seamless seal that covers the screw heads as well.
Around items such as the TV antenna, I cut the butyl rubber flush with the flange edge the cover generously with Dicor.
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