The process of drying boilies is essential to avoid instability, mould and actual spoilage.
In the chapter on how to make boilie, I strongly recommend freezing, but from your many questions I understand that many people have a preference for leaving the bait on racks or in breathable bags anyway, so we devote a bait guru pill to delving into the dynamics in practice.
The main enemy is humidity, which in the autumn and winter months can become really problematic, especially in those contexts that show the seasonal phenomena of fog (I'm thinking of the Po Valley in general).
Starting from the end of the cooking process, the first phase to deal with is cooling, which can be managed simply by spreading the baits on a cloth placed in the open air (in the case of a nice day) or by placing the baits on the drying containers and subjecting them to the passage of air forced by an electric fan.
The drying containers can be self-made racks or special perforated boxes, commonly sold for drying pasta. A truly low-cost alternative is represented by the perforated stackable crates that can be purchased at a derisory price from your local butcher or greengrocer, who usually recycles them or even disposes of them after use. This is an intelligent choice that does not require a special structure for stacking and are made of a material that can be easily sanitised after each use by spraying it with ethyl alcohol or bleach, then rinsing it with water.
After cooling, which usually takes a couple of hours, the drying phase begins, which lasts from a minimum of 2 days to infinity ... I can decide to leave on the dryer for months until the use arriving at balls as hard as cement that are also very useful for feeding as they counteract the attack of small fish.
I would like to open a parenthesis regarding the attraction of dehydrated bait, which is certainly less than that of freshly cooked wet bait, but which is irrelevant if I bait beforehand because the fish get used to that type of product anyway.
On the other hand, if I have to make a few baits for quick fishing, it is definitely better to freeze them after a couple of days of maximum drying.
In conclusion, to dry properly even in unfortunate places, it is better to have a closed drying room equipped with electric dehumidification.
The cheapest choice is indoor greenhouses, which can be purchased in various sizes for a few tens of euros, followed by PVC tool sheds and wooden or sheet metal garden sheds.
I have equipped a 3x3 metre wooden house because I prefer to do my odorous preparations outside the home... but this is obviously a personal choice also linked to the budget and municipal regulations for this type of structure.
Returning to the pvc greenhouse, a 2 x 1 metre model, where you can easily dry a couple of quintals of boilie, costs around thirty euros at the most.
At this point, inside, we will find our boxes stacked in good order, with a single layer of boilie per shelf, so that the air can circulate freely and we will have to equip the dryer with an electric humidity extractor, practically a machine that recirculates the air, condensing the humidity and collecting it in a drain pan.
Even here, the smallest models are obviously sufficient, as they are generally sized for a small room of a few square metres and cost a few dozen euros.
There are also more complex solutions, equipped with a moisture meter that can be programmed to start and stop automatically, these are more expensive and interesting perhaps to equip a small house like mine, where you can store not only a few tons of boilie, but also the equipment, preserving them from moisture damage.
If the equipment is simple, it is worth investing a few euros in a small hygrometer, which is an instrument that measures the humidity in the environment.
After 48 hours of drying, the humidity decreases drastically and you will realise that the machine collects less and less residual water. At this point you can transfer the baits into a freezer or watertight containers (as described in the specific chapter on the website about storage in buckets) or leave them in the dryer, starting the dehumidifier manually when needed.
From this point, the baits can be placed in breathable net bags, such as those for potatoes or those sold for this purpose and hung up, freeing the boxes for new productions.
In my book Boilies you will find a chapter dedicated to preservatives.
In the gallery you will find pictures of the various solutions.