That's basically it Duke, you have a good grasp of it .
In relation to your questions, firstly it's not always Paddy Power , it could be any number of bookies. So what I do/did is watch the bookies for specials that I see enough edge on . I then contact Betfair and ask them to put up that accumulator on Betfair (Betfair will put up any market if you ask them). I will seed the market on Betfair so if its an example like above a bookie offering 2/1 on a evens shot , what I will do is put 5000 up at 2.50/2.52/2.54/2.56/2.58 .
I then go on advantage gambling / money saving / stoozing /profit accumalator/ arbitrage type forums or facebook groups and post that this bet is available to lock in a guaranteed profit and link them the markets at Betfair + bookmakers.
I show people how much to stake to allow for commission to lock in a guaranteed profit.
What normally happens is i'll end up with about 15-20k matched at about 2.54 average, it depends how quick other professionals get involved , the professionals will never drive the price down to fair value because the better the arbitrage becomes the more the 10 pound punters talk about it now been worth 2 pound a shop and the more people will get involved multi shop / open gnome accounts etc to get on , so market forces mean the accumulators are always higher than fair value. I wouldn't want be risking 15-20k but I know early money is usually matched at highest prices so I then lay back off my money into the markets or offer a portion of my bet to other professionals I know.
I'm not afraid of sharing Duke because I've basically semi retired now , I worked intensely for the last 7/8 years and have lost interest don't need money any more and want to enjoy other things.
There are calculators online showing ideal staking size so as not to go broke , you input the odds you are getting and the odds it should be and it will give you the ideal stake, I ran my own verison of kelly criterion
http://www.albionresearch.com/kelly/ it wasn't as agressive as full Kelly. But stake sizing depending on odds is one of the most important factors imo.