i personally use an old copy of photoshop, but any drawing program with an aliased (pixel) brush is good enough if you know how to use it well. i've seen it done extremely well with firealpaca, paint tool sai (especially this one, shoutout toreodere), medibang, clip studio, gimp, etc etc etc. even ms paint once or twice!

having a good drawing software does help you out a lot, but you should put technique and comfort at the top of your list when going for that sort of style & MSPFAs.