As a beekeeper, here is my advice...
-Bee suits are not 100% effective against stings. They can sting through the fabric, and through whatever you have on underneath... within reason. I've had them go through the suit + a tshirt before. The big benefit of a full length suit is you have given them very few places to get inside the suit... ankles and wrists. Throw on some boots and long gloves, and you've got decent protection.
-If a full suit is too much hassle (working around other gear), you can get a jacket, or even just the veil. Full length jeans offer decent protection... especially if in boots, or tuck pants into socks. Then tuck shirt into pants, and put on the jacket. If you're really cheap, just a veil, a white shirt, elastics around your wrists. The ultimate goal is to keep them out of your face.
-Various types of smoke can be used. I've heard good things about whole tabacco leaf (if you can find a source of dry leaf). Old burlap bags are also a good one. Another option is a 1:1 mixture of sugar water in a spray bottle. Makes it harder for them to fly, and gives them something to do.
-If you can't get a beekeeper to do a 'trapout' on the tree, you might want to try this:
staple/tape/nail screen around the section of tree they're entering through. Best done early morning or late at night, when they are inside. If you do it during the middle of the day, you'll have "field bees" returning home that can't get in... and they will be cranky. A roll/pack of window screen is fairly cheap, and combined with some duct tape, will seal them in fairly well.
Then, assuming it's possible (every tree is different), try to find where the hollow section ends (on both ends), and cut the whole hollow section out. If this is on the ground, it's much easier for a beekeeper to do a trapout on it, or for them to load the whole thing in a trailer and take it home. Sometimes you drop the whole tree and cut it out on the ground... sometimes you cut the section off while still in the air and lower it down... every situation is different.
-If you really need to subdue the hive, consider soapy water. Bees covered in soapy water can't breathe, and will suffocate fairly quickly.
-check local laws... some places have passed laws making it illegal to 'exterminate' honey bee hives.
-If you must spray some sort of chemical on the bees, don't even bother calling a beekeeper. They won't want the bees. Sort of like pouring Draino down a sink to clear a clog, then calling a plumber... If you don't inform them, they could suffer serious health affects from the exposure to the chemical.
