One thing I've learned over the last 200 hours is that you Don't have to have as much micro as you think to get a level surface. The first time I sanded down the support I left a good layer of micro because i could see the skin starting to come through. However, I've learned that just seeing it doesn't mean your that close to it. So now After I filled the low areas I sanded the whole support down another mm or so and I'm very pleased.