Better quality of blades. Check JH brand Tajfun and Sprinter, Super Spirnter series. There also Pegas and Flying Dutchman
About this issue you perhaps buy blades for cutting frame not for ScrollSaw. They don't have reverse tooth.
I newer sand my works.
Another something... It was experiment base on a little accident with resin and idea of old/new method of shaping material.
First results was poor, bad... disappointment. But when try fill the crack the spill resin made surface transparent and pleasant look.
Its not great... but i find hope...