I've never had to do that before...
The powerhead of my engine has been sitting in our conservatory for about a month whilst I sort it out; the rest of the engine has been outside. When I looked at it yesterday a snail had got itself between the driveshaft and the middle section - right at the lowest point and.
I ended up using a length of PVC hose on the end of Henry the vacuum cleaner's* hose to grab it (and chuck it into the neighbour's garden
It must have taken ages for it to climb in there...
* Other brands of vacuum cleaners are available
"Can ye model it? For if ye can, ye understand it, and if ye canna, ye dinna!" - Lord kelvin