Still learning Beersmith and With adjust for equip checked it gives me 164 deg Strike Temp to get to 150 deg mash. Now do I should I just add that water and just immediately add grains and stir?
Yes and no. I use a Igloo 10 gal which is well dialed-in in Beersmith. BUT if it's cold outside, etc, Beersmith tends to run 1-3 degrees too cold in my experience.
What I would do is this:
1) See what Beersmith says your strike temp should be WITHOUT adjust for temperature. This tells you what the strike temp should be for the water + grains. This is important.
2) See what Beersmith says your strike temp should be WITH adjust for temperature. This gives you an idea of what it thinks your strike temp SHOULD be.
Now, I take temp #2 as a starting point. Let's call it 170. I would heat my water up to 173ish, add it to the cooler, shut the lid and give it some time (as long as it takes me to mill my grain and weigh my chemicals). Now I take my temp in the cooler and compare it to what beersmith gave me in #1. Let's call it 160. I always err on the side of warm, because it's a lot easier to lower the temp via ice cubes than it is to raise the temp via boiling water IMO.
So, if you water is around 162ish, you should be golden, just add your grains and stir. If it's too hot, add a couple ice cubes. That should get you to your target (150ish) once you dough in. If you are 1-2 higher than your target (since Beersmith said 160 and you went ahead and doughed in at 162), you can add a handful of ice cubes and move on with your life.
Now you can look back and compare what temp you started with (173 in this example) and compare it to Beersmith's value #2 (adjust for temp) to see how it worked and compensate in the future. After a few times I learned that I needed to shoot 3-4 degrees higher than BS's suggestion. Of course, ambient temps are always going to change, so I always went ahead and did all those calcs every time to be sure. I always went 3-5 degrees too warm and then used a few ice cubes to lower the temp as necessary.
Also, remember that your cooler is going to lose some heat over the course of the mash, so you might want to shoot for a initial temp 1-2 degrees over your target so your 150 mash doesn't end up at 146 at the 45 minute mark.
I hope that helps. Lots faster to explain this verbally than writing it out.
And this is a good argument for why I build a HERMS system - you just can't get a consistent, easily repeatable beer this way. But you can still make great beer!