From the camping area in alternative 2, follow the fairly obvious gash descending down and towards the river side of the dome. There were cairns there at the time. Basically, follow the most obvious way down (easy, not even third class) from the carpark, heading towards the front of the dome. You'll fairly quickly (5 minutes tops) get to the end. A nice big ledge atop some death slabs. Don't consider downclimbing or looking for sneaky ways down. Rap. Walk out to the end of the ledge, and you'll find two bolts with chains. Just rap. You'll get down to another pair of bolts shortly (we suspect a single 60 would reach these second bolts, but we were rapping on double 50s) From there we rapped 50 metres to the base of the slab. We also suspect that you could rap 30m and downscramble the lower portion of the slabs.
From here, you will be at the remains of a cable car? that used to cross Helm's Creek. It's a very easy slab walk down stream (and then some upscrambling) to get to the base of all the climbs on Power Dome. Water level might change this, but we didn't see much evidence of anywhere we walked being seasonally under water.
Instead of going all the way to the bolted anchor atop P3, consider building a gear anchor in the crack at the finish of P2. This leaves you directly beneath the opening moves of P4, making the traverse unnecessary.
I think you'll see that this is mentioned in the opening sentence for Pitch #3. Thanks for elaborating though....
If you park at the bend in the road, you can reach the base via rapell. Walk to the place where the slabs steepen (north end of dome) down climb to the point where a ledge system (approx 3 feet wide) starts across the slabs, walk this ledge to it's end. chain anchors will be found. You can then do one rap 165" to the start of the ledge system that traverses the entire face. Walk this, note some 5.5 climbing is found along this walk! You can break out the ropes and protect this section (small tcu's). go another 100 feet to a little corner system. climb up 35" (3rd class) and you are right by the start of "Welcome to..." .
I always do this approch, because one is wearing climbing boots anyway. The other way down is a scree slope with some loose junk that gets into your shoes. Bob Kamps showed me a variation to this that requires no rope, but you must have brass balls to do it! At the start of the 3 foot wide ledge look down about 60 feet. A small dike cuts across the slabs and leads to the landing spot of the rapell. down climb to this dike and traverse across the slabs, this is very exposed but it is solid. 5.2 XXX IMHO