Sediment broken free in pipes has likely caused lower water pressure

Does anyone here know what I can do about this? My house is old and has a combination of galvanized, brass and copper pipe and fittings. I went to fix a couple of leaky valves outside and I noticed the pipe was jam packed full of rust and calcium. I took the pipes apart and replaced them and installed new valves and now the water pressure at every faucet inside the house is really low. I'm almost sure that a bunch of crap broke free and got pushed down into the pipes in the house when I removed the old galvanized stuff outside.

Is there any way I can somehow clean the inside of the pipes or shoot pressurized water from say the shower head all the way back to outside the house? It's not just sediment trapped inside the shower head or strainers. There has got to be a chunk sitting at a 90* bend or something like that at some point in the house that's causing the problem.