Hi Shay

Is too easy, you just take a cylinder (almost all the drop tanks are circulars), then you place the cyliner over the background image, now put  each cross section where you need and begun to reduce each section to the final shape, thats all.

If the drop tank is oval, like the one of the F-86, in the frontal view just give to the cylinder the new shape.



Hope the info was useful

Regards