I second Jeff's opinion. The brake light switch isn't nearly as prone to going south as the column multi-switch. As you said, fiddling with the turn signal lever fixes the problem temporarily, that's your clue right there. Over time the contacts bend and wear out, in a few rare cases you can bend them back and keep going but I recommend a replacement. DIY it shouldn't be too much to spend but the fact that you're working with airbag components, removing the steering wheel...well, if you're not 110% confident you can do it, turn it over to a pro.