If theres one thing i know its skipping rope as I train at a professional boxing gym 6 days a week. Sorry to say this but i dont think there is any magic routine or advice that anyone here can teach you other than time spent skipping rope. Plain and simple.
I remember when I first started and like most people you feel like such a tool! but with perserverance you do get better. In the beginning what i found most difficult was to keep a rhythm going for any length of time before loosing concentration and timing.
After time though it becomes second nature and the mind muscle connection becomes so efficient that you start to “feel” the timing and can relax more which helps with rhythm and also endurance.
One piece of advice i can give is to vary the rhythm ie: dont just jump with both feet at the same time, but vary it by alternating between the feet.
Do you have problems with endurance eg: literally cant skip for more than 6 minutes? or is it more a case of you want to be able to skip for 6 minutes without making a mistake?