A couple of tips I can try to pass along may help with the future castings.
In using the Oomoo, I think you can mimic the 2 sided mold by doing the following, which should also cut down on the mess. The way i've casted this way, you will need disposable cups as the mold housing. In normal 2 part mold castings you use a vice or plates with a clamp/rubber bands to hold the sides together. The cup will keep the mold pressed together in the same way.
When making the mold with multiple parts, make sure the parts are in a line. Once the silicone has been set, use you hobby knife and cut along the line from end to end, going just deeper than the heads. I wouldn't cut the mold into 2 parts, but you could. Next, take the same or similar cup that the silicone was poured into to make the mold. Cut out the bottom of the cup and press the now empty mold into it. It should be a very snug fit. Depending on how full the cup was at casting, cut away the excess portion of the cup, leaving it the same size as the mold. When you flip it over, the silicone should be touching the surface and the casting holes should be up top. Before you cast, you might want to hot glue the bottom of the cup and mold to prevent leakage. You can also use clay.
So now when you cast with this, you can tear away the cup (if it was a dixie cup) and splay it open to get access to the resin items. Oomoo tends to tear, as you've seen, so just be careful with it, or use a hobby knife to cut away where you need to have the mold split (if that makes sense).
For extraction, i use forceps. It really helps on saving the mold and straining the fingers.
For the more flexible silicone, i only cut when i have to (like on complex pieces where the item has a hole through it and won't come out without tearing the mold. I still use the cup as a brace to prevent leakage.
For cleaning the syringes, good paper towels, wire, and plastic cutlwry are your best friends. Water doesnt remove all of the resin and the resin can still be in the syringe even though it appears clean. Remove the plunger and wipe off throughly with the paper towel. The towel shoild mop up most, if not all, the resin here. For the cylinder, wrap a towel around the handle of a plastic utensil and spin it around inside the syringe. It might take a towel or two, but it should absorb the resin. For the needle area, use a wire or plastic rod to extract or push out the excess resin, cleaning the rod off each time. You can use the plunger to force most of it out with air. The best way to go about this is to have the plunger removed and then press it to the base quickly. Remove plunger and repeat. Use the wire/rod to swab the area, and repeat until you area finding any resin on the rod. Obviously, clean the cylinder and plunger again. You can also leave a length of wire in the needle poking through to the cylinder to prevent any remaining resin from clogging the needle.
I have been meaning to post up pics of my process, but i havent had the need to cast and my desk is cluttered with painting projects. I'll try to annotate this later with ms paint examoles as i can't make them on my phone atm.
Keep up the good work!
Also, can you post up a pic of the molds?