Dean are supposed to be hard to get apart. When you're soldering, use the opposite deans on the one you're soldering - it will keep the contacts from moving if they get too hot. Like when doing a female deans for a batt, plug a male into it, this will also give you a place to hold it. This keep the contacts lined up. Try a pair of unsoldered deans - plug and unplug them, if yours are harder, you've had some contact movement due to overheating.
Secret to Deans is to pre-tin everything, the wire and the contact you're soldering too. Then putting wire on the contact is only a matter of melting the solder toigether and this should take just a few secs.
Also with female deans, start with the pos - its inside and easier to do 1st.