Sorry, I misunderstood where you were suggesting pieces might get lost. Another member somewhere warned of the danger of exactly that route of entry into the engine, so I heeded his wise advice by packing red cloth shop rags around the timing gear and chain. This route of stray parts entry is a risk whether one uses compressed air, rope/bungy or no combustion chamber filler.

An additional choice I made to minimize the risk of foreign material of any kind entering the engine was doing one cylinder bank at a time. I did my job outdoors in the driveway. I tarped the car at night and pulled 32" stretch-wrap over the hood to windshield gap to keep any rain/dust out.