Some generated geometry will be nearly unusable. To avoid this condition, you'll need to add sketches (on the same plane) and create new sketch entities.
You may be tempted to convert entities, but there may be many automatically generated splines. Try to replace with 3pt Arcs wherever possible.
Utilize Surface From Mesh command to convert a series of facets from a graphical body into a usable surface feature
Planar surface and Cylinders are the most reliable conversions
Only a few of the desired facets are required
Utilize this command to close gaps if needed. This generally won't be needed if you recreate the surfaces manually
Utilize Split-Line, Trim, and Delete Face to clean up surfaces that are unfit for final results
First create multiple offset reference planes, then insert a sketch upon each plane and utilize Intersection Curve to create an estimated cross-sectional sketch of the graphics body
These sketches may then be cleaned up and used to loft
NOTE: If the sketches have errors, you may be required to use them only as reference and sketch good geometry over them, making sure you don't accidentally constrain it to the original sketch