You can get a signal meter that updates immediately as you move the antenna. It has a little stubby on top that you can use if you don't attach a cable. Mine doesn't do 4G, but mostly voice and 3G is needed. It was about $200 a while back.
Here's another tip. Make sure you have a ground plane and vertical separation between inside and outside antennas! A diagonal separation seems to work best (outside antenna on top and not above your inside repeater)
If you are trying to use your phone as a tester for signal strength, keep in mind they don't update signal levels constantly.
Directional antennas need to be 1) Pointed in the right direction, 2) Rotated properly, and 3) Horizontally aligned.
Granted, you likely are not using a 3' directional, so it won't be quite as sensitive ;) The panels are easier than yagi's.