Efficiency is much more than sparge technique, though it is a factor. Crush and temperatures are major factors and poor crush and low temps during sparge can lead to poor sugar extraction. You need to try to get the temperature of the grain bed as close to 170 degrees during the sparge. This allows the sugar to be dissolved in the water without extracting tannins from the grain. The lower the temperature, the less sugar can dissolve into the sparge water. If your crush is poor, you just won't be able to obtain good conversion during the mash. Maybe try double crushing.
A batch sparge is pretty simple and this how I do it. I collect my first runnings and add sparge water at 180-185 for mashout, depending on the mash temperature. This brings the temperature of the grain bed close to 170. Stir, stir, stir, then stir some more. Let it sit for 10 minutes then vorlauf and lauter. Open the valve all the way and collect second runnings. I do two steps so I check the temperature of the grain bed and add in water at about 180 degrees and stir, stir, stir, then stir some more. Let sit for 10 minutes then vorlauf and lauter and collect third runnings with valve wide open. I get about 75-80% this way and it takes about 30 minutes.
For batch sparge, how open the valve is is irrelevant. The stirring dissolves all the sugar in the water, so there is no reason to drain slowly. For a fly sparge, you drain slowly because you do not want to disturb the filter the grain bed creates during the vorlauf and lauter stage of collecting first runnings. You want the water to disperse over all the grain and not create channels in the grain bed. Channels in the grain bed leave some of the grain bed "unwashed" with the sparge water, resulting in lower sugar collection.
Like I mentioned before, I wouldn't stress the numbers too much. Why does it matter if you get good beer? Sometimes equipment doesn't allow for a better efficiency, so just use more grain to compensate. Honestly, most homebrewers wouldnt notice the difference between 60% and 70% (70% is considered pretty good, in my opinion). Being good at homebrewing is knowing how to use your equipment to produce beers that you like consistently. It's not measured by how good your efficiency is; it's measured by how well you like your beer. It will take some time to dial in your equipment. Good luck and cheers.