Thanks for the tip bvia
Maybe due to the complexity of F310B shape de cockpit was not moulded in one single piece (like most of the F1 models) but in 6 small pieces that must be glued together
This will create various gaps between the pieces that even after all the primer and paint job may continue to be visible if not correctly treated.
I have decided not to follow the correct order of the instructions in order to correct this problem in a way I think is the better.
I took extremely care to assure that the parts are glued in the perfect position and will fit perfectly with the back part and engine cover.
After all pieces were glued I cover the gaps with putty and sand them till the entire surface was uniform.
The front session is now ready to be washed with blue and white soap and to receive two coats of white primer and three coats of paint.