Thankyou for your email - unfortunately you have stumbled upon one of the dilemmas of modern bike mechanics - you have probably already realised this by having a quick search on any of the popular bike forums, which are rife with creaking issues. We resisted doing a press fit bottom bracket for a long time as to try and protest against what bike manufacturers were doing, simply making manufacturing processes simpler and quicker for frames - whilst creating these issues - as component manufacturers we only saw the negatives . Alas the standard remained and we had to conform, but we weren't happy in doing plastic press fit cups installed independently of one other, a poor shortlife solution in our opinion - so we designed a locking system, much like a difflock, were the cups are tightened together to pull tight into the frame and also ensure one cup couldn't move and twist independently of the other, thus causing creaking.
This couldn't be done using plastic or resin, not only because we wanted them to lock together, but also wanting the bearings to be replaceable (as so many bb's are simply binned!), so we created an aluminium cup, the downside of that is tolerances, where a plastic cup will allow a little bit of give to the frame it is being installed, aluminium will not - so it is vital the frame it is being installed to is free of any dirt and grit, and also any paint or lacquer which may have been left from manufacturing as this can cause squeaks and creaks. Ensuring your frame is at its best before installation would eliminate that as source, also ensure the bb is fully clean, it is imperative in any press fit situation that surfaces are clinically clean - any interference from grit or dirt can cause problems later on - and any slight noise resonates through a hollow carbon frame.
As you mentioned grease is important, not too much though, as again it will attract dust and grit - ... - other points to check are pedal threads and pedal axles, chainring bolts can also cause creaking. You can also try and identify the creak, ensuring it is still there when pedalling out of the saddle, which eliminates saddle creak and seatpost creak, another common problem - also try flexing the bars a bit as dry stem bolts and faceplates can also create noise.
Apologies for the lengthy email, creaking is a particular annoyance to myself and something I strive to solve - sometimes it just goes, washing can help, or make it worse - as well as temperature changes, where you keep your bike night/day as grease viscosity can vary due to temperature. You could try a thicker grade grease.