It really depends on the condition of the soffet's and fascia's. as it is the prep that takes the time.
As alex has said, don't bother with a pressure washer, you'll risk damaging woodwork. You have WFP don't you??
Use that to wash down with, either that or a bucket & sponge and sugar soap.
Washing down IS important.
God....it would take a while to really go into detail of what you should be doing (and I do know what I'm talking about, prior to window cleaning I was apprenticed - properly apprenticed over 5 years I might add - and also ran my own company for several years.)
to be perfectly honest, if your skill level is DIY then give it a miss, there is so much more to painting than a bit of sandpaper, a tin of paint and a brush!
honestly Rich, unless you know what you are doing you will do an amateur job.
For a pro, fascia's & soffetts on say a standard semi would be about 2 days tops....though that might be spread over 3 days cause of drying between coats and so on.
A morning of prep (washing down, sealing & priming, sanding etc) 2 to 4 hours undercoating then the same for glossing.
Ian