"just do it"
they only get easier with more experience

start with transition runs (15min runs after a ride of an hour or more). all you need to do is run to the point where you feel warmed up for running and then stop.

when these start to feel familiar and easy, go after the bricks with more running time adding incrementally as you would for any other discipline (10%max)

I've heard different ideas on this and i dont kow which is better, but i'll share them with you.
(this is after you spend a few weeks doing a short run after a ride like tri ac said)
One idea is that you should always bike hard and only run a short distance i.e. a mile or two. then do a completely separate run work out and stick to that.
the other idea i've heard is to have "run dominate" and "bike dominate" bricks. for example one week do a 1-2 hour ride and 10-15minute run. Then at another time do 45-60 minute bike and a 30-45 minute run, or more.
I'd heard that the run dominate brick os "too hard on the body", but i tend to think when training for a race that is so hard on the body, doing a work out that is hard every once in a while might not be all that bad.

seemed like a GREAT idea at the time....this is as sore as I've ever been.

I was embarassed in my first triathlon to manage only a 7:30 pace for a 5K, when alone I could do a 6:00 pace. But with a lot of practice, running even just a little after biking hard (or easy) made it second nature. It still feels a little akward at first, but with a lot of practice you'll have little transition lag, but be able to maintain a pace closer to what you could do running alone. Just do it a lot.