Rob - DigitalArtWorks - I have three cross-hatch filters for my SLR and they can be purchased with minimum or maximum cross-hatches for 'starburt' effects. The best way to purchase them is to buy the filter with the least amount of cross-hatch, that way, if you want more sparkle, just screw on another filter. Depending on the angle on how the camera is held, you can control the 'flair' of the starburst. If trying this, I would definitely use a tripod for control.
SophieAndAva, I used to photograph equestrian horse competitions where there was tons of Swarovski crystals and the riders wanted to sparkle for the judges, therefore, I used three cross-hatch filters on top of each other but I would recommend that you use a single , too much sparkle in a picture is distracting. Also, the neat thing about a cross-hatch is that with sparkles, you can see how the light prisms through the crystal giving a natural look over a photoshop enhanced sparkle.
(Here I am giving photo advice and my pictures look like crap! - that's why I wanted to join this team to learn to take better pictures with a point - n - shoot camera, I have two SLRs and a darkroom, so I'm old school)