What cbt techniques can I use in an anxiety and overwhelm spiral when I have to be with other people

This is a great question. As an introvert, you probably feel recharged after spending time on your own and may feel drained after being in a group of people. This is all very normal. Cognitive Behavioral Therapy, or CBT, helps us learn the ways that our thoughts and behaviors are linked. Broadly, CBT encourages us to challenge our distorted thoughts and notice patterns of thought that may be holding us back. I think there are a few techniques from CBT that can be useful to you here. 

First, Thought Stopping or Replacing is a very useful technique. When you are in a group and becoming anxious or overwhelmed, you may start to have thoughts like "This is too much," "I can't do this," "I'll never get out of this," or however the anxiety shows up in your thoughts for you (thoughts are different for everyone!). Having thoughts like this is very normal, but it can become unhelpful when it increases your feelings of anxiety or disrupts your work or relationships in the moment, which it sounds like maybe the case for you. With Thought Stopping, you use your mind to pause that particular unhelpful thought and prevent it from escalating. Some people find it helpful to picture a stop sign or imagine hearing a bell ring. Then, you want to focus your mind on something around you or a more helpful thought. For example, you may want to refocus on the conversation you are having or a neutral sound in your environment. You can also practice replacing the unhelpful thought with something more realistic, like "I can deal with this a little longer." I do want to mention that thought stopping and thought replacing can be challenging. It is best to practice these techniques in an environment that is low-pressure like perhaps your long solo walks. 

Deep breathing is a very helpful relaxation technique that can be done even when other people are around. Since you practice some breathing techniques already, you make take to this one easily. To do a very simple and inconspicuous breathing exercise, just breathe in through your nose and let your belly expand with air. When your lungs are full, pause, and then exhale slowly through your mouth. Notice your belly going back in. Repeat a few times until you feel calmer. 

Finally, I would encourage you to challenge the belief that being at work or around family means that you cannot spend any time alone. Think of it this way - if your colleagues are all together and one person begins coughing, they may excuse themselves to step outside for a moment, get a glass of water, etc. The same applies to you. If you are among your family or friends or coworkers and you start to feel overwhelmed, it is okay to excuse yourself for a few minutes, go outside or somewhere private to recharge, and then come back. The length of time that you can be away of course depends on your situation. However, you may find that even spending 60 seconds somewhere quiet will help you reorient yourself. You don't need to explain in detail why you are stepping away. A simple "I need to step outside for a moment" is perfectly acceptable. I have also worked with clients who pretended to take calls or reply to emails or text messages. 

If you'd like to learn more about these techniques or others, a mental health professional with training in CBT could be very helpful. Best of luck to you.