buy a small bore pump (the best way i find to keep them is to wrap them in news paper and keep them in a cool box with one ice pack, which you should change about every eight hour's this way they will keep fresh over night).
It`s always a bit difficult trying to explain such things....much easier to show you,but i do it as follows,and never miss a worm
Once you`ve found a nice cast and blow hole,take to spits of sand from in front of them,then a final spit from behind.The first spit is more of a "pilot hole" and should start around 8" in front,the 2nd spit should be taken from around 2" in front,giving you clearance for your final spit...the final spit is obviously very important,and should start around 2" behind the cast n blow hole,but you must make sure that your spade goes down straight,otherwise you`ll cut a lot of worms.The temp` dictates how deep the worms are,but even in summer,they can be pretty deep on some beaches,so make sure you get your spade well down....it`s that last part that many diggers fall down on...to my mind,there`s no point wasting previous effort by not giving a bit more on the final spit.
If you find that you`re cutting worms,then you`re either digging too close from in front or behind the cast,or not putting your final spade in straight.
You can pump blow lug,but it is much better in water....place the pump directly between the cast and blow hole and pump straight down...a gentler approach is required for blow,as opposed to black lug,as it`s much softer/fragile.
You can keep blow lug in good condition for a few days.Either wrap in newspaper (don`t overcrowd it) and keep in the fridge,or keep it in a bucket of fresh sea water...again keeping them cool is the vital part....add a cool block each day to the water.,and change the water (removing any dead/blown worms)daily.
i use a small bore pump for blow lug and i go straight down the blow hole about three inches. and it gets the lug with one pump nearly all the time without damaging the worm, and it doe's not hurt your back.
Marsh Tackle ( www.marshtackle.com ) make stainless steel bait pumps Themselves to order. Really tough and they work well. They have a small bore so you dont have to struggle sucking up a bucket of sand! I paid £20 a ccouple of years ago.