Hi Howard. Yes you would place the baking soda first. Don't make it to thick or the ca won't go all the way through. The way you have been doing is okay all so. Try the ca and baking soda on some scrap. Smack it with a hammer, I think you will find it super strong.
I used lipos 9v for the engine and 12 volt for the servos. I had to use voltage regulators. Those lipos last a very long time. This was my first time using lipos. Main thing is to keep a eye on your voltage. I use a voltwatch on all my planes. Most stores have them.
Good luck