Here's my unlined fretless, which gives me joy.
I follow 1,2,4 fingering below the mid harmonic and 1,2,3 or 1,2,3,4 above, just for intonation reasons. On fretted bass I use 1,2,3,4.
I also daily bow upright for intonation practise. I use a tuner and sometimes drone. Recording is useful to really hear your intonation. Takes work, it is very easy to develop a 'lazy ear'. Bach on fretless is great for playing all over the board, it will get you comfortable with all the notes on your bass.

Intonation is a life long challenge! Nice when things sound good.