As for the Rankin boulder, head over the forestry track at Talnotry. Take the bridge over the Palnure burn, past the junction. You then have two options: 1) Park at the first layby and head due East for 250m through rough terrain to reach the wall and head North for another 100m to reach the Tintin, Haddock and Snowy boulders. 2) Park at the 3rd layby (in the area where trees have been cleared, just after the stone snowman (yes, really)), then head East aiming for the wall and two distinctive mini crags past that. You should pick up the forwarder track quickly and the excellent Calculus boulder can be reached with a relatively easy 15 minute walk. From there walk Northwards maintaining the same height until you reach the distinctive roofed slab that is the Thompsons boulder. From there you can head North again and descend to the Tintin boulder if your skin is up for more punishment and the full circuit!