As a obsessive converter (i.e no model left stock!) one of the key thing I struggle with is cables, pipes and tentacles. You either bodge something together from fingerprint-laden putty, or use guitar strings which are notoriously tough to work with at this scale. So in comes this simple yet ingenious product. Normally retailing at £13.30 (as of writing it's on sale at £10.64) this is on the pricier end for a tool. You get three pairs of textured panels (small, medium and large ridges) and two guide bars, which snap on to the plates to give you a perfectly straight slide every time. The guides will need to be taken off if you want to get a more adventurous texture.
Operation is very simple. Place a pre-rolled out piece of green stuff or putty (ideally coated in Vaseline or another lubricant to prevent gumming up the grooves) in between the plates of your choice and start moving one panel side to side parallel to the guide bars. Top top, use the smooth sides of the plates to get an even thickness.
Here's something I made earlier. A few rolls turned this unloved Wraith body into a chaotic Mechanicus creation. This is a must-buy for any serious converter. It makes the difficult task of finding the right cable and positioning it just right that much easier. It's the most I've spend on such a specific tool, but now I have one I don;'t know how I made it this far without one.