Francis,
The layout method you choose depends more on the quality of material than your abilities. If your timbers are crowned, twisted or out of square than edge rule/square rule will be frustrating and will yield poor results without some serious planing. We use edge rule at Heartwood but our timbers are always within 1/16" - 1/8" of square and wind (twist) over 12' in length or we go to snap line square rule, as we would with hewn timbers. There are some good articles on this method in the Guild's Journal "Timber Framing". For severely wonky timbers we would then go to scribe rule. Good luck.