Remove all the loose and peeling paint. You will have to do some hand sanding as well. Sand to smooth the rough edges that are left behind after scraping.
Now that the surfaces are sanded, wipe them down with a clean cloth (rag) and water to remove the dust. All of the surfaces will need repriming before painting. Use a good oil based primer. Something that dries fast will be helpful, speed things up a bit. You can still use the finish paint that you have over the oil based primer.