A soft sponge and windex, the windex will break down the wax without harming the paint, follow with liquid soap and water. Always test in an inconspicuous area first.
I asked what to use on satin black hoods several months ago. There were some products mentioned, that I do not recall--do a search here.........................MOUse warm or hot water an dawn to remove any wax build up.........not sure what to use for a sealer though........might want to ask anyone that has the "satin" paint on their vehicle...sometime reffered to as matte finish to see what they use if anything at all.................