That would have to be one damn sharp blade. I’ve never seen it done before. 36 grit on a hard block… surform… electric planer… but never with a block plane.
I used a Stanley mini-plane once on a close tolerance blank that I was afraid I'd thin too much with a power planer. Anyway, not that hard to do. Make sure it's really sharp as NJSurfer stated, andjust run the plane with the blade set shallow, barely shaving the crust and at about a 45 degree angle to your run. If you get it right the crust should come off in big curls similar to wood when planed.
You've got the basic tools to do the job. Look for a shaping video on You Tube or I reccomend John Carpers' Shaping 101. Carpers's DVD is basic and easily understood. Electric planer to remove the skin. Small hand plane to bring down the stringer. Surform to clean up cuts and tails left by the Electric Planer. You can use the Electric OR the Surform for the rails. Finish it off with the sanding block and various grits of sandpaper and screen. Shallow cuts with the Electric. Assuming the depth adjustment has not been altered on the Electric. When using the Surform; Pull it toward you rather than pushing it away from you. More control. This is only mean't to be a rough summary to get you started.
I used the method above to “tune” my block planer (Helluvu lot of work). It actually made the planer work, whereas before doing this it would just snag and gap the foam. Even after tuning the planer, you really have to get the technique down when using it on foam.
I still wound up just using the surfoam as it removed material more evenly.
Set your planer at about 1/16''. With the blank bottom up on your rack, put the shoe of the planer on the corner of the tail. The baseplate should be hanging off the side of the blank, and angled about 45 degrees out from the centerline of blank. Hit the trigger and push the tool up the rail following the outline. You'll be putting pressure on shoe at first but quickly transferring to mostly baseplate push. Keep the angle about 45 d (a side-effect of this is that the cut is narrower than the width of the blade, because blade is angled). Go all the way to nose, turn around and and repeat back towards tail. Shoe rides one uncut foam, blades and base are riding on previous pass. Each pass follows outline a little less until you get to straight at center. Then do other side. Repeat if necessary, lol, that blank has a lot of meat in it.
If your first passes come out with some ridges or bumps, just set your planer near zero and block. Or just use a sanding block to clean up before you take another cut. The baseplate needs a clean line to ride on.