I got the lightweight cover to use in the Summer for overnight 'pre-car show' protection after I've detailed the car. This week I needed to dry my 'Ultimate' cover ready for today, so thought I'd test out the lightweight one a few days ago - that was the first time it'd been out of its bag.
I've never had trouble getting the ultimate cover back in its storage bag, it just takes a bit of folding familiarity and getting the last bit of air out with a bear hug. I use the car's roof as my folding platform with the following as my method of choice. Imagine wrapping a piece of cake in a tissue ... All clips/straps off and stowed. Fold cover from the bonnet up and backwards to the middle of the roof. Fold from the rear up and forwards to the middle of the roof. Lift each side upwards so that they too meet in the middle of the roof. Now fold the remaining side material up and to the centre. By this time the cover will be the width of the car's roof and overhanging front a rear windscreens a bit. Fold entire cover in half again so that you now have a long flat sausage about as wide as the storage bag. Fold inwards from the ends, expelling air as you go by gently pressing the cover against the car's roof as you go. Remove the now rolled up cover and give it a bear-hug before squeezing into the storage bag, zipping up slowly - Bob's yer uncle!