You can use acrylic paints to prime the inside of the gourd, using even coats, about two would do it. Then you can go ahead and paint your design or picture. The surface of the inside is a little porous and holds paint well.
The pulp of the Higuera is easy to take out if it is done when the gourd is still in its green color state. You can use a spoon and scoop it out. Seed are still unformed, and you are able to scrap all the soft fiber away from the wood like skin. If you got it all it will dry white. Put it in the sun for a while. Or you can start working on it right away. I have found that letting the water go out of the skin a little, stops it from warping later on when you carve into it.
Late summer in Puerto Rico is when you start to see these fruit like gourds growing in abundance on trees along side many a road ways, or cow pasture, or abandoned lot.
When the have reached maturity they fall to the ground most often than not in tact. Where they stay until, rotted or someone harvests them. The best time to collect these however is before they become dry and still have their glossy green skin.
They are much easier to open and clean and sculpt or carve. Plus they tend to smell when they are dry rotted on the ground. The pulp turns black, sometimes mold grows, and insects inhabit the gourds.
This tropical plant is known as Higuera, it is a gourd that grows on spindly long leaved trees in pUERTO RICO but can be found almost in all caribbean islands. Native peoples in times passed used it as washing utencils, cups, bowls, containers. I have recollections of using this myself as a child in the island of Trinidad . Today they are mainly used for craft items with some nostalgic , sourveniers type utencils being sold in stores.