i agree i think i just simply brush with paper and sand. but i done one badge yesterday i layed resin second layer and dam those dirty bubles and i thought o what to do i had home heater i put near that my pieces and everything gone. so i try on other parts but i think mystery starts to be solved it mean temperature doing this. so i post what happening on my amg panels that i do.

ive had this problem recently , maybe also as the temperature drops. In my case the results looked pretty good until i started to get down to polishing and the micro bubbles filled with white polish dust. just like yours. the bubbles are so small as to not be a problem if it where not for the dust in them.. but i found a way of getting the dust out... washing had no effect so desperate i tried thin oil (wd40) and rubbed it over the micro bubbles.. the oil managed to get into them and the dust has almost completely disappeared.  there may be other problems associated with rubbing wd40 onto your epoxy but i havent noticed any yet.

i tryed all ways but i found something interesting maybe that gonna work. today i thought dam it acted the same and surface like with dusk - but i turned heater a little and everything corrected. may that be of temperature as these nonsences never showed when was plus 25 now only 12.

Sometimes when you dip the brush to hard into the resin you will create little air bubble... maybe soft and gentle dipping might help...also degassing is always a good idea.

and et the end part looking shiny and nice but inside these small bubles.

why it camed like on photo? when you brush very tiny bubles are left on part?

and what is sad that this happening on after 3 layer or more after brushing paper and cleaning. what to do now? to brush with water pape and relay one again? as that was last layers.