Having started on fretless electric bass a while ago (I never really played fretted), and more recently switched to DB, I found that the following things were of use for the switch. I don't know if this will be of use or interest, but just in case:
1. Having practiced BG with a hand position like
this (from
this article). This meant I was used to keeping my hand in a consistent shape to aid intonation, and moving the whole hand around smoothly.
2. Using Simandl fingering (1-2-4) in lower positions on the BG, particularly for 5ths and octaves. This was more comfortable and avoided stretching which could result in going out of tune. Guitar fingering was fine higher up.
3. Having a map in my head so that I could "see" where the notes were without having to look at lines on the fingerboard and using only side dots as a guide as necessary.
4. Being used to listening to correct intonation.
I am far from being a skilled player, but one thing which leads me to think the above helped was playing a tape of my first bass gig (on fretless BG in 1995) to my DB teacher. His remark was that he thought the intonation good, though the choice of notes was questionable on occasion.