It’s interesting that Walter G. finds it works best with a smooth surface, I find just the opposite.
Been a long time since we had a Form1, but our Form 1+ and our Form2s release the build much easier if the build platforms are a bit rough. With the Form 1+ I used to sand the platform with 150 grit sandpaper using small circular motions and then clean with a paper towel and IPA. The Form2 platform comes with a bead blasted finish and it released its build rather easily until that blasted surface smoothed out.
My current process is to take a utility knife blade in hand (not in the blade holder but just holding the blade itself). I scrape the blade across the platform, with the blade perpendicular to the platform using the entire sharpened edge to scrape it. This removes oxidation on the aluminum and give the surface some “bite”. I clean it off with IPA after I scrape it. My prints release very easily from a platform prepared this way.
One note, the blades can pick up bits of aluminum that stick to them and it does not do as nice a job as a rather fresh blade. You will feel the difference between a fresh blade and one that has aluminum bits stuck to it. I guess you could remove the stuck aluminum bits, I just pitch the old blade and use a new one.