If you do find a swarm hanging on a branch etc just waiting to be collected get hold of a 400 x 400 x 400 carboard box , use duct tape to remaqke it into a box .
Nick a corner off to give a 25 mm hole , shake or scoop the bees in , close it up and stand it in the shade till you can go back at night and bring the swarm to you own hive .
Shake them in your spare hive , block the entrance with foam to leave a few mm gap at one end or stuff it with fresh pulled grass for a day , feed the hive from the top with a simple screw top jam jar feeder .
Or if you have a neuc box shake them in over a full set of frames after sunset and again feed the neuc box.
At one period of my life it was not unusual for me to have six or seven such cardboard boxes each well wrapped in muslin cloth that contained a swarm of bees in the back of my estate car as I travelled back to my small holding ( wearing the full bee suit whilst driving ) . I chose the carboard boxes because they folded flat and were easy to get hold of from work .
One thing ..... After a period of cool wet weather when the swarms havn't been able to leave the hive as soon as they can , they usually go to hang on a low bough etc in the shade out of the rain, then you'll often find the queen has gone on her queen a mating flight whilst the weather is good , she comes back to the swarm on the bough , may stay there for three or four days till the weather improves and her girls find a new home or the birds etc decimate the swarm .
If you collect a swarm at this stage of events the swarm will scarper back to their original hive if near enough or sometimes will re swarm when the newly mated queen is escorted back to the swarm on the branch & they fly off to a location they have recently sussed out .
If you collect and transport the now queenless swarm they will be confused ,angry & tend to smell like fresh crushed nettles. If you have been feeding them all is not lost , you can unite them to a queen right hive using a sheet of newspaper to separate above a queen excluder , an empty super , shake them into the frameless super at night , now add on a queen excluder and a few supers , then the rest of the hive.
After three or four days the queenless swarm will have accepted the queenright hives pherome signature of the resident queen and the queen right bees will have accepted the new bees as their own . Now take the hive apart remove the frameless super and rebuild the hive , taking care to place the supers in the same original orientation.
It is an amazing sight to see a newly mated queen coming back to a hanging swarm or a hive with several male genitalia hanging off her back end .