If you don''t mind advice from a newbie, here goes:
Your post is a little unclear. When you say, "sail thru a close hauled to a 180 dg. downwind", I''m assuming you are tacking through the eye of the wind, then falling off on the other tack to a run. For starters, if all you want to do is go from close hauled (approx. 45 degrees to the true wind) to a dead run (180 degrees from true wind), you could simply bear way (steer away from the wind without tacking through the wind) while easing your main and jib sheets to maintain proper trim. If you do need to tack first, you simply tack through as usual, but then ease the sheets as you bear away on the other tack.
Once you get the wind a fair amount abaft the beam, the sails are no longer acting as airfoils (keeping to a simple explanation). This is where you need to present as much surface area perpendicular to the apparent wind as possible. In a deep broad reach, your mainsail will be out most (or all) of the way, depending upon how far you can allow the boom out (spreaders, shrouds, etc. may get in the way).
Running dead downwind is not always the best choice (IMHO). You would either have to try to keep the jib full on the opposite side of the main (running "wing and wing"), or it will be ineffective being blanketed by the main if on the same side. Using a spinnaker is a different story, but I''m assuming you''re not using one yet.
A lot of folks jibe from a deep broad reach on one tack to another. To do that safely in a larger boat, I was taught to maintain control of the main by trimming the boom to near the center line, then slowly jibing the boat (steering her so the wind comes from one side across the stern to the other). Near the center of the turn, the main will catch the wind on the opposite side and come around, but it only has a little ways to go and can''t build up appreciable momentum. Letting a large main swing from all the way on one side to another is a recipe for disaster in many situations. Since the apparent wind is often low, on small boats it is not uncommon to control the main by carefully throwing it over by hand, without actually sheeting it in all the way. Use good judgement or get some competent instruction if you are in doubt.
When you say you lose the wind, it may simply be that the apparent wind has dropped so much that it seems that way. As a simple example, sailing at 6 knots into a 10 knot wind will feel like apporximately 14 knots on your face. Run dead downwind with the same wind and boat speeds and you have an apparent wind of only 4 knots. Four knots will feel like nothing compared to 14.
Hope this helps.