Hello Maximus
I had a barium meal a couple of years ago. My experience was that I was assisted in swallowing a tube which was fed down my intestines to my bowel. A chalky liquid was then poured down the tube directly into my bowel. They then took xrays of the area. Shortly afterwards I needed the loo a number of times. The stool was very heavy and chalky, this lasted about 2 days. Other than this there were no side effects.
I have heard though that some people drink the barium meal, but this then obviously has to pass through your system. With mine they wanted it to go staright to my bowel.
Im sure others will be along soon to give you their experiences.