If your issue is that the lens in a hatch is leaking, then you should just remove and rebed the lens...using only silicone, unless the OEM has a different specific recommendation. It's a simple job, the work is mostly removing the old sealant from the lens and the alu frame. Get those clean, and resetting the lens is a piece of cake, and it will last for many years. Smearing a coat on top may not be successful, and is not likely to look too good.
Certified...in several regards...