I am coming from winging and tow foiling, very comfortable on foil at this point, and looking expand my skill set. No experience surfing but want to learn to prone foil.
Is there any utility in learning to surf first without a foil? Looking for any guidance on set ups, reading waves, conditions and techniques. Thanks.
Winging in waves will give you the wave reading knowledge. You don’t need to go to longboarding first. I would just wing in waves if I was you. 
Catching waves with a foil is bloody difficult even for very accomplished surfers. The positive being that you can skip the surfing and dive straight in, just be patient and start small. Also, put some work into finding a wave with a gulley so the wave breaks and then fades
No.
The skills partially transfer between surf and prone.
But if you want to learn proning, then prone, don’t surf.
One of the most beneficial things about learning to surf before proning is learning etiquette, who has the right of way, etc… Especially if you are planning on going to a mixed spot.
So many people with bad manners at the peak on foils, simply because they dont know basic surf etiquette.
Worth it to learn the culture around entering a lineup, and to be able to develop a natural sense of who has priority at any given time. This of course matters more if you’re surfing spots around other surfers, rather than just foilers.
As for speeding up the learning curve on just wave riding ability prone foiling, I’m not super sure it’s worth it vs just getting time on the foil. Some of the body movements translate, but the stance really doesn’t, the takeoff is pretty different, and the lines you take on the wave are very, very different.
I would argue that my progression was slightly hampered for a few months by trying to take such surfy (high) lines in the pocket of the wave because of how long I’ve been surfing. Those same lines do not work well on a high aspect foil.
You should surf for the love of it. It is fun. There is no tips and trick to be learn in the internet that will be more valuable than to spend as much time in the water as possible. Good wave, bad wave, blue bird sky, pissing rain… just go out!
If you just want to learn to surf to get better at foiling, I’ll suggest you dont do it. Spend all your time prone foiling. You will get your oceans knowledge anyway.
Only thing I can say is etiquette and safety of yourself and others is a high priorit
. Especially if you arefoiling around others. You will definitely wipe out. You need to be highly aware of how that will affect others around you. Also knowing about tides, swell period, rips, currents is very important. There is alot going on and it is not something to take lightly. Learning how to surf would definitely help but not necessary. Just be humble and think about all possible acsnarios as you enter the water. Be highly considerate of others. You are riding a much more dangerous vehicle than a surfboard.
Wear a leash!!!
I don’t know why you’d want to learn to prone foil if you can’t surf. Way easier ways of catching waves on foil… that said, if you were able to learn to prone foil without a surfing background, you’d probably be able to longboard surf about as good as anyone within a day!
My take is…..Any water time helps. So surfing would definitely be positive as has been noted above, for etiquette in the line up, reading waves, safe entry and exit points etc. But for any sport the best way to get better at it is to do that sport. Enjoy!