All answers are spot on, I just want to add a couple of tiny details.
You set your pedal tension to low (something like max tight minus 8 clicks). You ride for a week clipping and unclipping often. It becomes intuitive already ... but never quite as easy as flats. Now what?
Well, now do never forget that you can ride SPDs unclipped! When starting at a busy intersection you could pedal with the arch of the foot. There's no cleat there and you are effectively using the pedal like a slightly uncomfortable flat pedal. Then clip in after you have cleared the stressful intersection. Same applies for sections of MTB track where you think you might need to dab.
Now about unclipping technique. You need to twist your foot to unclip, move it to the side to clear the pedal and then step down, right? That's 3 movements, compared to only one for flats.
Wrong! Do move your foot diagonally! Initially leading with the heel chose a point on the ground to the side of the pedal and just step there, unclipping will happen as part of just stepping to the side of the bike. After a week of experience you will be able to unclip and step in a single swift movement! Still some miliseconds slower then flats (or arch-of-the-foot) and higher cognitive load but very close.