It’s not as difficult as it looks. If the leaf is moist, the top of the vein can be separated not easily but it’s not incredibly time consuming. Not all Maduro wrappers have large veins though and most can be worked out with a roller or doing as we are talking about. I’ve dealt with a number of large veins and it’s led me to try numerous rollers. A small wood roller is the very best, a rolling pin will work but it’s often harder to control. Next would be a phenolic resin or plastic roller. I bought a metal roller that’s used for wall paper but I don’t recommend it unless you have some way of smoothing out the ridges in it. The edges are also sharp enough that if you are successful in flattening the vein, you’ll also put what will become a tear line in the wrapper. I’ll experiment this evening and see how a disposable razor does.