how to prepare for a drive-mapping of "destination" and traffic signs? (best practices)

Some people use Vespucci and apparently you can download the area of interest prior to your outing so you don't need to waste your mobile data plan.

I often use OsmTracker for which I've set up a custom button set that simply has quick action buttons for speed limits, stop signs, and traffic lights. Pretty easy to use the GPX tracks in JOSM to spot the places that speed limits change, etc.

But recently I've found that I just pull the microSD card out of my GPS enabled dash camera and fast forward through the videos. When I see something of interest (bus stop, bench, traffic lights, speed limit signs, destination signs, stores, etc.) I use the lat/lon on the video to zoom to the location using JOSM, verify the imagery matches what I expect, and then add or update the objects in OSM. A down side to this is the dash cam is only looking forward and there is an amazing amount of stuff that just doesn't show up like you might expect (like many shop name signs). We recently took a two day holiday into the local mountains covering about 300 KM and it took me maybe 4 hours to do all the OSM editing afterward. One reason it was so slow to map was that the route relations for several of the highways we took were in sad shape. In addition to actually fixing the areas that should have been dual carriageways it took me a while to get the route relations fixed up.