Many times I have seen fastener stretch increase 50% just by cycling it a few times. I loosen the bolt completely (this allows the lube to be redistributed from one side of the threads to the high pressure side) and push in new lube under the bolt head. Initially and when you are getting close to the desired number it is a good idea to remove the bolt completely, clean the threads and re-apply new assembly lube. The goal is to get as much rotational energy into stretching rather than lost in head/thread friction. I dont go over the maximum recommended torque, I think they list this to avoid running the risk of over twisting the fastener.

It does take a while to get the hang of using the gauge. Also, you can affect the reading by changing or putting too much tension on the gauge. If your gauge has a needle sharp tip like mine did, rounding it slightly may help it find the center of the bolt to get a more accurate reading.

BTW, all this takes a good bit of time and I doubt most shops go to the trouble.