Agreed on no cereal in the milk. I had many people suggest that to me and I didn't do it and was glad I didn't. The pediatrician actually told me it can cause juvenile diabetes or diabetes later in life. Also, it's a choking hazard as well.
As far as him not liking the spoon, I wouldn't force it because at 8 months, he is still getting all the nutrients he needs from the formula or breast milk- it's really just practice for him. You might just be offering him solids when he is already full or he just isn't in the mood. Try something for three days, then give it a rest. Oh, and my mother said out of all the cereals, all of us liked the barley the best, and the same went for my daughter. Barley cereal was her favorite, but it had to be mixed with some type of fruit. I'd try just a tiny bit of cereal mixed in with some carrots or applesauce right before he gets his bottle just to see if it is because he is already full. If that doesn't work, just give him a break from the solids for a little while and try again in a week or so. I hope this helped.