For general pests sometimes it makes sense to do it yourself, but for termites I don't think so, and this doesn't mean hiring a "cheap" exterminator to do local treatments or "removing" infested wood by saying it solved the problem. But if you want to postpone a professional treatments consider the following:
1. if you have severe subterranean termite infestation, in any case only a professional complete treatment around the house and in all possible access points makes sense. In this case I wouldn't recommend self-treatments. If it seems not that severe then lots of things in your house can kill subterranean termites if you see there, the problem is reaching to the colony which is 5-10 feet deep in soil. So, if you just want to exterminate those whom you see since they irritate you realize it won't solve the problem at all and spray whatever you want.
2. For drywood termites which live inside the wood, you may experiment some "self-treatments", but most likely will end up calling a professional in a year or so because they will pop-up in another area. These are less dangerous though compared the subs I mentioned above. Again, if you are able to reach them that's what it takes. I wouldn't go but these Home Depot "termite extermination materials", they are just chemicals and you will breath them. Drywood termites if reached are very weak, their strength is their ability to live inside the wood where no insect can completely go. But if you are able to drill and introduce anything that will bother them, it will kill them, and yes even water. So, if you see droppings coming, find out where the studs are, drill holes no more than 3 inch apart and say inject vinegar which won't damage your health.