The technique for playing the Cor Anglais is perhaps more different to the oboe than you might expect. You need far far more diaphragm support - the instrument is physically longer, so you have to push a heck of a lot more air through it, so really, the first thing you should think about is getting a big, full sound. Really push and give lots of support.
I say this cautiously, but for starters, forget the notes, the tuning etc...try and make the biggest, fullest sound you can.
Once you have this support, then start addressing tuning and whatnot..
Also, the embouchure needs to be considered - the reed is larger than an oboe reed, so make sure you aren't squeezing you lips too hard together - this will restrict the vibration, and consequentially the sound quality and projection.
As a side note, make sure you are using a good reed. (indeed, the bane of every double-reed player!). Perhaps you could check with an oboe/cor anglais teacher on this.
Hopefully there is some useful info here!
Re: English Horn trouble 07:52 on Tuesday, May 08, 2007