Frustrated with inability to do body work!

Spent some time the last 2 nights working on the door. Here are some pics of what I am encountering. Not sure I am doing this correctly.
After the first layer of filler and as seen in the previous post I laid down a solid 6"-8" wide filler application. I tried not to get it to thick.
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Getting ready to sand some of this. I am sanding using an 11" block with 180 grit to start. Once I get it fairly smooth I switch to a 180 grit.
View attachment 1715108829 Below you can see where I am at after doing 3 coats and resand. Trying to use a different color each coat so I can see when i get tot the previous layer.
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Heres where I stopped for the night. It feels very good but I have to do a thin coat using a glazing putty? there are a few scratches that need filled. My question would be how thick do I apply the glaze and how do you tell how thick you are putting it on. how far above and below the previous filler do I apply the glaze. Trying to learn and do this the correct way.
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Thanks for any advice you can throw my way.
Rod

Typically I hit the first coat of plastic with 40g on a long board or air file., then sucessive coats with 80g all the way up until it's straight. Then skim coat with polyester glaze and switch up to 180g. If you start blocking too early with 180g you start to waffle it back up. When it gets to the final coats of plastic coat and work the whole area each time. Putting a little swipe of filler in the middle of it and sanding it makes it worse. Do you have a long board?