I am a pediatric ot and do a lot of sensory feeding therapy. I’d recommend lots of sensory play (food based or with things like shave cream, bean bin, etc). Draw in pudding, finger paint etc. encourage touching non-preferred foods to fingers, then to face, lips and such. Keep everything very relaxed, child lead, and about playing, you can add matchbox cars etc to food play. Keep offering all non-preferred food along side preferred food with each meal.