There are several ways to lay out the cuts. Here is one that can work for a DIY.

The basic wall from the top view ...

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For the start at one end of the wall, if the end of the cap will be seen you will want to do a broken finish with the same overhang that will be on the wall face.

Once this is done, lay the block into position as shown below.

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On the underside of the block mark at the front intersection of the wall block and also at the back at the half way point of the gap (blue spots). Remove the cap, using the marks scribe the line shown in green and saw the block.

Set the finished cap back into position on the wall. Set a piece of cap block where the next one goes to act as a spacer as shown below.

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Set the cap to be cut on top of the spacer so that it overlaps above the last block cut as shown below.

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On the underside, mark the cap at front and back to match the previous cut block (blue spots). Remove the cap, scribe the green line between the marks and cut. Set the block back on the wall and return to the appropriate step above to cut the other end.

that looks pretty good to me!! may try that...
I had seen some weird formula about dividing the distance after placing the caps and having them touch at the front corner as well....those pics are a great help!

Before you go to all that trouble see if you block has a radian cap that is already shaped so the caps can follow a bend.

Ah! you liked that idea Steve eh? too simple, not simple enough?