My way of search:
Get to a nebula
Look for landable volcanic bodies with a temperature >200K and <500K, if you find one then look for ejecta craters on it (use system map image for that). I prefer bodies with radius of 1000km or less because the craters are easier to check.
If area has been checked before by other pilots this website can help you to find candidate quickly
https://www.spansh.co.uk/bodies/search/C8BAEB6E-BE2A-11E7-B6AA-9472C33B8412
If there are ejecta craters then do a glide above them as shown here: (the BT POI is shown at 2 minutes, but you may as well watch the whole clip to see how to find things)
https://youtu.be/VNVyGoEJF5w?t=123
(BT POI on ice planets is different, it is small POI as with geysers, no shrinking, so it is bit more difficult to find, but ice bodies with temperature over 200K are quite rare, so no need to worry)
Now my gut feeling is - if you are inside nebula and you found BTs means there are Ancient Ruins around so then you start checking every system in the area. I use this way -
https://youtu.be/zIhbu_AYmDU
I look for BTs first because it is 100 times easier to find a BT than to find Ancient Ruins, with trees you know exactly where will they be.