Please, not pairing. This is the worst practice ever invented in software development.
It does not deliver as much value as code reviews does and it cost much more the code review in terms of time.
Generally pair programming is designed for below average programmers who are not competent enough to work on their own and who afraid of their work to be visible and attributable to them by others. Your best developers will probably leave if you try to force it in your organisation that did not have them before and I know many really good developers who will avoid getting a job in an organisation that has pair programming.
Code reviews can be organised quite well if your Tech Lead have people’s skills and know what he is doing.
My advice on how to ensure code reviews are not painful: http://sceptical-meerkat.blogspot.co.uk/2017/01/code-reviews.html