If you live near the Texas Medical Center, Debra Bootin, MD is great ###-###-####).
What baby book are you reading this information?
If I'm understanding you right, you're asking about feeding cereal through a bottle. I wouldn't suggest it. Starting solids is training not only your baby's digestive system to accept solids but also training your baby to eat from a spoon and feeling the new textures of solid food in his/her mouth.
Here's my experience with nursing and solids:
Babies' main source of nutrition is still milk for the first year. I breastfeed my 7mo son and started him on solids at 5.5 months also. I nurse him with a full feed and then 30-60min later, I feed him solids. It is the same schedule for daycare, bottle first, solids later. It is fine if my son doesn't finish eating all his solids which is supplemental to his nutrition.
Week 1, I started at 0.5 tablespoon rice cereal (Earth's Best) with 2 tablespoons expressed breast milk for a soupy consistency. Every 2-3 days, I slowly increased the portion of rice cereal while watching my son's behavior. He becomes uninterested, turns away, or closes his lips together when he is full. Week 2, I increased to 1 tablespoon rice cereal and 1 tablespoon sweet potato. Every 4 days, I introduce a new veggie or fruit (squash, bananas, avocado, peas, green beans) to watch for any allergic reactions.
I started introducing solids at breakfast. After 4 weeks, I added solids to his lunch feeding session. Of course, your feeding schedule is all based on your baby's behavior and appetite. You want your baby to know when s/he is full and can self regulate that appetite and not overfeed your baby. I had to cut back on his portion size after he nursed for a shorter time. I hestitate to add solids at dinner to avoid disturbing his sleep with gas, upset tummy, allergic reaction during the night. Eventually, dinner solids will be included but I'm not in a rush. We're still training him on other foods.
I make baby food which turns out to be easier than I thought. The book, "Super Baby Food" by Ruth Yaron is a great reference. As a nursing mom, do not follow Yaron's nursing advice. I am protective about my nursing (and paranoid about preventing low supply) and prioritize nursing above solids.
How often to breastfeed depends on your baby and your parenting style. How often are your nursing now? There is no true right answer to this question. It's specific to your baby and your feeding routine. At 5.5 months, my son was nursing every 3 hours. After I introduced solids, he smoothly transitioned to nursing every 4 hours. But remember, I fed him solids 30-60min after nursing a full feed.
This is just my experience. There are other moms who may have advice that's better suited for you.
Just remember, start slow with solids. Look for allergic reactions. Nursing is first priority. Designate a specific time and location for feeding solids so your baby learns to expect the new routine. Watch for your baby's cues when s/he is full. Make feeding solids fun with lots of smiles and encouragement. I clap, sing, make animal noises, say "open" to prime my son for the next spoonful, etc.
Pump while you're at work. Kellymom.com has some great advice. In general, pump in routine intervals, for example every 3 hours. This will maintain your supply while away from your baby. I started pumping every 3 hours and now every 4 hours. And to be safe (and super paranoid), I pump before I go to bed to avoid a long stretch between nursing session. My son dropped his late night feed and I want to maintain my supply still.
Wow. I had alot to say. Please update us on your new and exciting adventure with solids. I'm still learning too.