As you are finding, it depends on the paper and chemicals.
Some times you are stuck with the long exposure because of the paper, and there is really very little or nothing that you can do about it.

On the M600 you can put in a 150 watt bulb, for more light. I use my M600 with a 75 watt bulb, because the 150 watt bulb is TOO bright, and results in very short exposure times. Then swap back the 75 watt bulb after you are done with the print using the 150 watt bulb. The smaller wattage also generates less heat.