The 'blue blaze' that Bill is talking about is actually a red-circle-on-white blaze for the Ramapo-Dunderberg trail. It shares treadway with the AT from Tiorati to Fingerboard shelter. The A-T turns right and the R-D continues straight. Takes you straight to the Tuxedo train station. It's a longish walk, (I don't have my mileage table handy, but I want to say it's six or seven miles from Tiorati.) There are a couple of shelters on the way (Bald Rocks and Tom Jones, if I recall correctly).
Tom Jones is the oldest shelter in the park, and still has a great feel to it. It and Bald Rocks both have attractive views, and the R-D is a ridge-walk across whalebacks with the occasional sweeping view. Bald Rocks has a water source about 1/4 mile down the yellow-blazed Dunning Trail. The nearest water for Tom Jones is a stream that's by the parking area on Route 106 about a half mile before the shelter. The best water option for Fingerboard is to tank up at the bathhouse at Tiorati. Surebridge Brook is closer, but the water tastes terrible and originates in the tailings pond of an old iron mine, so I can't imagine it's that good for you, either.
From Tuxedo you can take a train into Manhattan, and then hop the subway across town from Penn to Grand Central for the train back to Pawling.
Another possibility for easy train travel would be to take the A-T across 17 to the junction with the blue-blazed Sapphire Trail, turn right and take that trail a couple or three miles along the ridge parallel to 17. It comes out right at the Harriman train station.
Either the Short Line bus or the train is much cheaper than any kind of shuttle option you'll find. If you must have a car shuttle, Village Taxi in Monroe will pick up at any Harriman trailhead within 10 miles of Route 17.
This is all from memory because I don't have my maps and mileage tables handy, so take it with a grain of salt.