When I hear /ue/ at the end of a base word, I often write ‘ew’. There are a few words like ‘skewer’ and ‘news’ where the /ue/ is not quite at the end but I still use ‘ew’.  When I hear /ue/ on its own in a syllable or at the end of a syllable, I write ‘u’. When I spell, I listen for bases and suffixes. I have to check the base to see if I need to apply a suffixing rule before adding the suffix.