Karen, the only time you need to bring up the bobbin thread is on a domestic machine when you load the bobbin for the first time. You can stop and start as many times as you want without touching the bobbin again until it runs out of thread. Then load up a new bobbin and continue sewing. Use needle down when you want to reposition the fabric, like turning a corner, without losing the position of the last stitch.
If you are talking about a longarm machine, the rules are different. PM me if that is the case and I can walk you through that.
Hope that helps.