If the only task that frequently requires accurate torque limiting is tightening clamp bolts at the seatpost, stem, and handlebars, I'd check to see if they require similar torque values (maybe 1nm of variance). I'd then consider a torque key like:
this at a value that does not exceed the value of any of the parts. These are inexpensive and easy to use. Otherwise, I have
Amazon.com: Effetto Mariposa Giustaforza II 2-16 Pro Torque Wrench Red, One Size: Automotive , but that's probably nicer than you (or I) actually need. But some kind of low torque click torque wrench is good for these kinds of things.
I use Finish Line Fiber grip. It works fine; I have not used any competing products. It can also be useful for clamping aluminum handlebars, and to reduce the torque needed to secure threaded steerer wedges.