I resealed two windows on my motor home Saturday. I used a sharp putty knife to remove the old putty then applied a coat of
Motsenbocker's Liftoff Product Link to remove the caulk from the siding. I finished off carefully cleaning with some Acetone.
On one window, the previous owner had used some bathroom caulk over the existing caulk. Removing it was very easy.
I use
Geocel 28100V Pro Flex Crystal Clear RV Flexible Sealant. Instructions say use a soapy water mix with your finishing tool to distribute and smooth out the Pro Flex sealant. My finishing tool is a finger which I wipe excess sealant with a rag. Learned that trick from a friend of mine that caulks professionally.
The Geocel Pro Flex comes in a variety of colors too!