I would expect your bilge pump to be close to the transom, if so, then that's the ticket. And it's sitting on a 1/2 inch tall pad, so not much will remain.
If you have some minor oil /grease in there, get a pig or the bilge cleaning solution, pour into bilge, run the garden hose in there for a minute or two, then stew it around a bit while on a ride, then drop the hammer.
Since the lowest part of the bilge may not be the transom at rest, at lot of water can come from up forward.
This process will get it all since the various compartments are piped together. My 252 has 5 bulkheads crossing the keel, all five are interconnected.