In a responce to cruichin, I mentioned that he should consider using a building board to minimimze handling the model and to aid in positioning the model to work on it. The building board can be used to hold the parts for painting and to give you a level horizontal plane to work from. Some stick & string ship modelers use something similar to hold their work in progress.
I make my building boards out of pine boards. This one for a 1:350 scale USCGC Hamilton is made from 1x4 and is about 6 inches longer than the ship. Size yours appropriately.
I put some block legs on the bottom to raise it off the surface. They were glued and nailed with some finish nails.
I drilled some holes to match up with the mounting hardware previously installed in the hull and ran some bolts up through the bottom of the board ...
... and through some tube standoffs into the bottom of the hull
I attached an end piece to one end (1x4 and about 6 inches long - size yours appropriately)
It is attached with some screws so that I can swap ends with it if I need to get close to one of the ends.
In use, the building board can hold the ship upright (first picture), or laid on its side using the upright to keep the ship & board from falling over
You can stand the ship on its end using the upright on the end as a base. Clamp the upright to your table for added security.
And the board can be rotated on the upright to help you access hard to reach areas.
Hope these pictures give you some ideas on a building board fixture