Do you create the MDPI drawable first and just scale it accordinly to the .075/1.00/1.50/2 ratio by pixels in photoshop or do you recreate each individual drawable?
I use Inkscape, working with vector images as well, then export to the required raster size for the various resolutions. An article I wrote on producing icons from Inkscape can be found at https://tekeye.uk/android/android-launcher-icons-using-inkscape