Inspect the surface area for holes, cracks or other problems and apply acrylic caulk to fill them in. Use a putty knife to smooth out the caulk and remove any excess to prevent bumps. For particularly thin or narrow crevices, you may have to use your finger to smooth out the caulk. Caulk contracts and shrinks, so apply a second layer once it's dried.
Being in the business for 25+ years I have had the privilege of working with thousands of clients. Although they all came from different circumstances and backgrounds they all had one common goal in mind. Every one of them wanted to be respected, receive top value for their money, and get the best possible paint job for their most prized possession, their house!