Give him a
bath. Warm water up to his arm pits making sure his vent is fully submerged... Baths are key here, and an un happy beardie is better than an impacted beardie! Beside if he really doesn't like it, the splashing around and trying to get out just may promote a bowel movement.
If you really must, then just use a larger container in his tank. Just be sure the water is deep enough to submerge his vent completely.
If nothing passes after just a few min in the water, you can try to very gently massage the right side of his belly with your finger, starting at his arm pit and making very gentle circular motions down to his vent feeling for any hard lumps.
If all else fails you can try feeding some unsweetened apple sauce, or a couple drops of olive oil either directly by mouth, on a cricket, or in his salad. This will act as a laxitive and help get things moving along.
Repeat the baths daily until he stools.