Paper patching increases the size of a boolit by a few thousandths. So take a receipt from your last grocery store purchase, tightly roll it around a boolit until it is ~0.004” larger than as-cast diameter, turn & twist the tail, roll it in bullet lube (Vaseline or chapstick would work too), press it into a case, use a bullet puller to get the boolit out. Now the case is larger than an as-cast boolit, and makes for a nice cookie cutter.