if you can pull the paint/clear off by hand it may be better for the long run to just strip those panels to bare metal and start over. to do so you would use some good aircraft stripper, then immediately spray with a metal etching primer of some sort. then start your mud work and cover it with a good high build urethane primer.
I have never used eastwoods paint but haven't heard anything bad about it. ppg shopline products are not very expensive for what you get in product but most people dont realize what it costs in materials to paint a vehicle the proper way. I just did my truck and my grandfathers 79 f100 last year and we used shop line on the f100 and it came out nice but still spent right at 1k for primer, sealer, base, clear, filler, easy sand putty, and sanding materials.
On the blocks i would go as big as the surface would allow and still be able to move around easily. on most hoods, doors, bedsides, tailgates I like to use a 18-24" long block for the big areas and around the edges and curves use a small 4-6" soft block. for the hard to reach places ill use a piece of soft foam cut in a half circle and put a piece of 6" da paper on and use that also. its all in what you're comfortable with.
If this is your first all over paint job, I would stick with the gloss. the flat primer look is ok for a beater IMHO. Most people dont realize with flat what it looks like when you are finished is what the vehicle will always look like. (unless you re-spray it of course) Base/clear or single stage has a lot of forgiveness in the final product if you know someone good with a buffer. I have used PPg essentials single stage in the past in it has awesome durability, comes in tons of colors, (even metallics) and has a very good gloss to it. I actually just sprayed it on my personal short bed project and it came out awesome! the best part depending on the color is price though as you can get a gallon kit for the sub 175.00 price range retail i believe. hope this helps
James