Getting a good grip is a constant challenge, changing with the conditions and the shot.
It took me lots of practicing with candy plastic and experimenting with grip aids before I used it in less than perfect conditions. The worst conditions are cold and wet with a hand which is cold and wet on a forehand drive through a tight tunnel. Compare that to a nice, warm dry day on an easy backhand upshot. But we have all had even easy shots slip out (when we grip too softly) or griplock (when we grip too tightly).
The liquid grip aids mentioned in the OP were around a decade ago when, in desperation, I tried every product I could find. As I recall they came in two basic types, an antiperspirant and a grip enhancer (sold for the sport of bowling). Neither worked very well for me. But I also tried dirt, fruit juice, saliva, chalk (rock climbing), birdie bags ( which made discs MORE slippery to me), pine tar (reasonably effective but dirty and near impossible to remove from under fingernails), synthetic pine tar (aerosol spray) and probably a few others.
I used a synthetic pine tar product called Pow'r Tac (sold for baseball and racquet sports) for years and only recently stopped using it when I found a better solution: factory grip stamps. If you search Pow'r Tac on this site I have described the details of its use, benefits and limitations in prior posts.
For putters a hot stamp can be burned in deep enough and placed where your rest your thumb on top and fingers on the bottom that the plastic surface is no longer smooth and gives a superb grip. For drivers a knurling tool, heated up, can create the same effect on the inside rim. I have encouraged my beloved sponsor Discraft to make these widely available as I think they would be popular. I get a lot of positive remarks from players who try out my discs.
PDGA regulations disallow post production modifications of discs but do not restrict what the FACTORY can do. I think knurling of the interior rim should be made legal as there is no difference between what a factory can do and what someone could do with a tool on their own. A knurled interior rim does not affect the flight of the discs at all. It only makes it easier to get a good grip. A good grip is not just a performance issue, it is also a SAFETY issue. A player is more likely to endanger other golfers or park users when conditions make a good grip hard to get.
No matter the grip aid you use, it takes a lot of practice to know how to use it, perfect its use in differing conditions and gain confidence in it. Aside from Factory stamps/knurling, all other methods break down in terrible weather for forehand shots (at least with my grip).