Just put some engine oil or trans fluid in the cylinder bores and shoot some oil in the passage for the initial clean, put on stand and then cover with a big ole trash bag. Then have the shop hot tank then clean all over again. Moroso have some passage brushes for cleaing. It won't rust. Did this myself during my engine build. I rolled mine to the drive way and armed with dish detergent, moroso cleaing brushes and water hose cleaned the block after I got it back from the machine shop - still dirty. Used air compressor to get rid of water and then oil everything up again and covered the block with a big ole trash bag. No problems.