Dear Subscriber, I have used Ashburn products before myself, with very good results.  Mostly because they service their products very well, at least the group out of Houston did.   As far as mixing coolant and water, were not talking about acid and water here, so safety is not an issue.  Some metalworking fluids mix readily with water, and others need more encouragement, such as vegetable oil based fluids.  We want mixing, which means we want the highest possible Reynold's Number for the system, i.e., you want turbulence.  Turbulence results in better mixing every time.  Using a commercially available mixing nozzle is best.  If you don't have one, streaming water at city pressure, (higher velocity factor), for a longer period of time (since you will be adding more water than coolant) into a vessel containing the smaller quantity of coolant would be best.  This is true unless the source of the water flow is allowed to be blocked by the rising water level, thereby reducing the turbulence.  Prevent this if you can.  Another way is to pour the coolant in at the point you are blasting the water into the tank.  But you said you are using a bucket to mix a petroleum based product, so I assume this is make up concentrate to increase the concentration in the tank.  Get a paint stick, no big deal.  Ashburn 9500 mixes easily with water anyway.