Nothing personal, but people who powerwash for a living aren't exactly a high IQ crowd, and the fact that you seem to think there is only one way to do things indicates that you're not objective enough to take completely seriously.
Wow. I spent 14 years in corporate America in high tech software sales. Now we own our own business...An entrpreneur in a blue collar trade does not mean that entrepreneur is an idiot. As a matter of fact, Tony (A-Plus) who responded has a hi tech background as well, and if I recall correctly, has his MCSE.
There is more to this, than just starting an engine and ripping up wood. The best of solutions are not in Home Depot, and where wood is concerned, you develop an eye for detail and craftsmanship. I urge you to read the link I posted above, before making any more hasty generalizations about the professionals who do this daily for a living, with pride and professional results.
As fo the choices you presented. I would choose none of them since the one that fits most closely as described will do damage. You need the appropriate cleaners and neutralizers, you need to drop the pressure at the tip - you won't find help for that at HD or Lowes, nor do they stock an array of tips. You will not in all likelihood accomplish this without scarring your deck and raising the grain to the point of it needing sanding, and if you sand it, there is a good chance you'll do that wrong simply by choice of the wrong grit paper. I'll bet if you do this yourself you won't think about wearing PPE, and could end up exposing yourself to carsinogenic substances. For example, oxylic acid is often used to neutralize and brighten, especially on cedar. It also can cause sterility if you are exposed to it.
Cedar, is a softwood.
One of the easiest woods to damage. In fact, you can do it as simply as digging into it with a fingernail. Go try it, see how easy the wood scars, then ask yourself if you really want to hit that softwood with ....2,500 - 3,500 PSI or whatever your machine from the hardware store is rated for, since you don't have the right tip to drop the pressure, and no idea how to do this correctly. Every year i personally see countless decks damaged by owners who think they can save a buck, then call in the pro to fix it and don't understand why it costs more to undo damage than it does to care for a deck that was in good shape before they touched it.
We let the chems do the brunt of the work. The machine is used to rinse. It's a process, and there is education for those who learn this trade.
Since you are not doing this yourself, you should look for a pro who is:
Familiar with a two step cleaning process - includes cleaning/or stripping as needed followed by neutralization
Doesn't wash with pressure over 1,000 PSI
Can tell you about the properties of cedar
Knows proper preparatory steps prior to sealing the wood
Doesn't buy selaer from HD or Lowes
If sanding, doesn't sand with higher than 80 grit.
Any professional should be able to expalin the process to you thoroughly, in a way that makes sense. Get references.
Beth
p.s. if we all seem to be saying the same thing it is because we do have an authority we listen to.
http://www.fpl.fs.fed.us/