When given a choice, select a ductile rather than a cast adapter. Some, but not all explosion proof motors are available with a C or D frame end bell. Check with your supplier. If you do not have a C or D frame adapter you will be involved in the last three steps of the four-step procedure. You can hit the motor with a big hammer, but small dimensions are hard to get with this method.
Some people use an adjusting wheel that attaches to shims.
Another method is to use an adjusting wheel that slips over the motor hold down bolts. Many mechanics make there own tools and these units also work very well for precise motor movement. You do it on your automobile when you notice uneven tire wear or the car drifts to one side of the road when you loosen your grip on the wheel, and have no problem justifying the cost and time involved. It is the same logic you use towards the added cost and time spent balancing the tires and wheels of your car. We do not always apply the same logic to our very expensive rotating equipment in the shop, but we should.