The way I explain downwind settings in my seminars is condensed to the following:
Put wind telltales on the tip of the bow sprit, on each bridle fly and on the sidestays.
1) Start sailing downwind with the bow sprit telltale at about 90 degrees to the boat. Trim the spin so the spin telltales are flowing (for sure the leeward side)
2) Trim in the jib until it stalls (backside telltales not flowing aft) and ease until the backside telltales flow.
3) Bring in the mainsail traveler until lower mainsail telltales stall, then ease until they flow.
4) Sheet the main until the upper telltales stall, then ease until they flow.
5) Use a laundry marker and mark all sheets. That way you already know all the settings and can easily get your rig in the ball park. Minor adjustment from there.

When sailing you will see the bowsprit telltale is still at 90 degrees, the bridle telltales will show a closer reach and the sidestay telltales will appear as a close reach or even upwind.

Once the sails are set that all the sail telltales will react the same way. So, you simply have to read one set and you are reading them all. Now you simply have to sail by the sail telltales.

Good luck,
Rick