I open SCI Companion, open the game, open the pictures tab, find the one I want, export it to PNG, open the PNG in Aseprite, shit all over it, and save. I then go back to SCI Companion with the picture still open, click Import, select the edited PNG file, pick "Map to current palette", select all but the last color, click the refresh button, confirm the preview is correct, and hit Accept. Then I do File, Export as patch file, and save as in the case of PQ1, 4.p56, in the PQ1 folder.