I have used both the plastic primer and the normal grey primer on my Skelly paint jobs, and to be honest did not find a noticable difference between them with regards to finish, however I did find the normal primer flowed much more easily from the can.
One thing I would do is sand down more with a finer grade of paper as the sanding so far looks like it needs to be smoother for a more even finish (might just be the photos so apologise if this is the case.
As plastic is semi porous, grease from your fingers is a big problem, wear rubber cloves at all times in sanding and wash all parts in mild water/detergent then rinse in water and air dry before painting or you will end up with the dreaded alligator skin effect. Seriously i can't stress this bit highly enough. if you get it the only way to get rid of it is to sand back to raw plastic and start again.
2 tins of primer should be enough for the frame, with sanding in between to flatten off, and perhaps 3 cans of top coat applied over time with drying and sanding in between coats (probably get 4-5 coats out of the 3 cans)
Logo wise, how about making a stencil for either the cowling or the mesh side panel?
Hope all goes well, and happy to help if needed.