I'll jump in as well.
A combination bit can be great for a lot of horses - It can also be very confusing for a lot of horses. It exerts pressure on every part of the face - The mouth, the nose, the chin, the poll. This can be too much for some sensitive horses, or can be ideal for horses who are too sensitive in the mouth.
If you do want to soften him up, I don't think the combination bit is the tool for the job. It is easiest and simplest to soften a horse up in a snaffle - As it sends very clear signals, and any release is communicated quickly and clearly to the mouth. It is harder to get a clear release with so many pressure points on a combination bit - And it is the release that teaches, not the pressure.
The combination bit may well work for him after you have softened him up and have him going well.