S.H.
I've never heard of that "solution" for diaper rash.
If a baby won't eat, they won't eat. She is simply probably not ready.
At this age, "eating" is an INTRODUCTION to foods, not eating feasts 3 times daily, like adults.
A serving size for a baby this age is in terms of teaspoons or tablespoons...NOT "jars."
I can't believe your Pediatrician suggested you feeding her solids and then not giving you further information on it or WHY he/she suggested this for curing diaper rash.
Some parents put a little rice cereal in a baby bottle, then make the opening a little larger in the nipple so that the cereal mixed milk/formula can be sucked through the nipple.
BUT, you REALLY need to ask your Pediatrician. He/she should be telling you what foods to start with, how to go about it, and what to do.
SOME babies at this age, still have a "gag reflex" and their tongue will still push out the food... they will not yet "swallow." You cannot make this reflex go away, until THEY are ready for solids and can swallow.
ALSO very important, is to remember that for the first year of life, a baby's PRIMARY source of nutrition is from breastmilk/formula...NOT solids.
Also, if you are breastfeeding, it could very well be something you are eating and thus may be in the breastmilk, and the diaper rash could be in relation to this.
If her diaper rash is not going away... has your Doctor examined your baby? Sometimes it is a yeast infection and standard diaper creams will not work on this.
Some babies get a diaper rash when they are teething too.
ALSO, if your baby is not eating....it could be perhaps due to teething, or "Thrush" in her mouth.
In any event, I would think your Doctor would look into these other POSSIBLE causes and factors.
All the best,
Susan