If the nappies/wraps are new, don't attempt to do anything to them! PUL is waterproof as it comes, you don't and shouldn't need to do anything to them at all.
If you do and they're still under warranty, get them sorted by the manufacturer! If they're preloved, I still wouldn't do anything to them unless you have problems. Some things shouldn't be tumble dried and that is the way I usually see people suggesting you reseal PUL... however, tumbling something that shouldn't be tumble dried can ruin the PUL in the first place, so you may be doing more harm than good. I actually very much doubt that tumbling PUL can reseal it anyway. Wild Child explains it pretty well I think - http://shop.wildchildnappies.com.au/pages.php?pageid=11 Basically if you're getting PUL hot enough to reseal it, you're more likely to do damage because of the pulling action of the machine. I wouldn't tumble minky at all.