I don't think your irritating can be healed by better pre-shave preparation. You can have next issues:
1. Stropping, you haven't mentioned that you have strop and use that you using it.
2. Dry soap, to prevent it from drying try to lather one part shave it, than lather second and shave it. It's best option for the start.
3. Most common issue. Maybe you apply to much pressure, try to give razor short, light strokes, don't apply pressure at all, razor might find it way under razor weight. Try different angles.

Irritations on the neck usually the biggest, it's the most difficult part to shave.

You need good honed razor, no pressure, wet lather, try different angles and clear irritationless shave will come with time.