Personally I believe the issue of snail baits is overstated. Try as I may, I cannot find direct reference or actual details of the oft quoted incident of a bluetongue having died as a result of eating baited snails. The reality is that these are quick acting poisons and any snail or slug with them in their system would be dead with a few hours. So if you can keep your snails alive for a day, then they will definitely not contain any poison from baits.
Of possible concern might be some of the toxins that occur naturally in some garden plants. I really don’t know. If this possibility worries you, then simply keep you snails for a week or so while what is in their system passes through. Snail purge what is in the intestines within two days, hence commercially they are starved for three days (to be on the safe side) prior to cooking.
I’ve found the easiest way to collect them is from people’s front yards, as they like to feed on lawn grasses. Front lawns with a shrub border are best, as the snails can shelter and get protection amongst the shrubs during the day and, being nocturnal, move out onto the lawn area to feed at night. The best time is in the early morning light before sunrise, while it is humid. They can also be collected by torchlight in the evening. On very overcast days, particularly if it rains, they come out earlier and stay out longer.
There’s many different ways to keep them. For me, they were they were most easily stored in a plastic tub or bin that can be firmly sealed shut and is well ventilated. You can use a soldering iron to make lots of holes or, alternatively, melt a piece of metal flyscreen into the lid. Don’t use plastic screens as they can eat their way through it. Include a shallow saucer of water and always keep in a cool spot out of direct sunlight.
If not fed, most will go into ‘hibernation’ sealing themselves up and becoming inactive. Or you can feed them on green lettuce leaves, apple, bran, carrot and the like. I used get my snail food from the ‘throw out’ bin at the local supermarket. I’d simply ask if it was OK to “take a bag home for my birds” ( saves on lengthy explanations) and was never refused. Active snails produce lots of wastes, so they require regular cleaning. A gentle spray with water followed by tipping out of wastes does the trick. To reduce the frequency of the need to clean you can include layers of newspaper covering the bottom of the container. I sometimes added crumpled pages from glossy advertising magazines to provide more space for the snails to occupy. They seem to like eating the starch used on the glossy pages.