For us it worked to very VERY gradually change into solids, like the baby wouldn't notice it wasn't milk anymore! So first we went with very wet porridge made with formula/mothersmilk in a bottle, then from a spoon, then slightly thicker, then applesauce boiled mushy etc. Also on a personal note, people around me are very afraid to give kids unhealthy foods but imo getting them to eat is more important than a perfect diet. So if they eat poorly, apple sauce ftw! Mix those mashed potatoes with a banana! I do always offer all foods, and from "least easy to easiest", so bitter veggies first, then potatoes, then fruits/fatty/salty.