Rain Gutter Sealing

Good morning, Guys!
As I am going over the project (71 Dart) in excruciating detail, I have noticed a couple of small areas where I need to repair some of the sealer used in the rain gutter. The vast majority of the existing sealer is in great condition, so I only want to repair what is split or pulled away. I am thinking that I can use masking tape to create a boundary on the sheet metal. What product have you guys used in a similar repair? Any tips on using the sealer or the process you used to fix yours? Thanks for your help! L8r

Jim