NOTE: This info has been substantially updated.
RCPs are largely, not entirely, drawn. This is a gross deficiency of Archicad in it's current form. GS has to fix it, we can't. (It wouldn't be hard, though.)
The trouble arises because model elements overhead in plan, such as beams, are shown with a dotted line. The same elements should be solid in the RCP. The reverse is true for elements such as counters. They are solid in plan, but sometimes it's helpful to show them dashed in the RCP. There's no display option or element attribute to handle this.
This leaves you drawing beams with a solid line and counters with a dashed line in the RCP, using the true elements as a guide. Awful.
There are workarounds, but they're all drawing lines, all tainted by original sin.
At least you can show the crown objects.
Finish fills also need to be added, just like floor finish fills.
For simple ceilings, you can combine the electrical and RCP. If the ceilings are complex, separate them. In this case, it is sometimes desirable to show the lights with the RCP. Put the lights on E Fixture2. You should still hide the switches, switch paths, and alignment lines. Electrical plans need their own post.
RCP techniques:
You can draw any line you want. Here's some ways to draw lines faster.
Stair lines: Show the Stair2 lines. Marquee their area. Find & Select for the stair lines (Pen, Layer). Copy the lines in place. Keep the selection as it is; don't drop it! Switch the pen (n3), layer (+A RCP Line), and linetype (dense dashed).
Soffit beams or slabs: Select the model elements. Copy them in place. Keep the selection. Switch the pen (n3), layer (+A RCP Line), and linetype (solid). Explode (Cmd+=).
You can do slabs and beams (and whatever else) at the same time: Select and copy the model elements. Use edit selection set (Cmd+Opt+T) to switch the pen (n3), and the layer (+A RCP Line). Tricky: to change the linetype, open the settings for each element type by double-clicking the toolbar button. Explode.
Counters, decks, and terraces: Just like the soffit slabs above. Use the dense dashed linetype.
Roof overhead: Do the first. Copy the roof outline from the roof plan down to the floor below, then change the layer. Copy the dashed overhead lines in the plan, then switch the layer and the linetype.
REMEMBER! All these lines are dumb. If you modify the model, they just sit there getting wronger and wronger. There is no workaround for you maintaining the accuracy of this work.