I just figured this out, so I'm quite pleased with myself.
1. Go weed in the garden for half an hour. There's no sense wasting all this effort on babies who are only technically dirty.
2. Set the babies in the kitchen to shed large chunks of mud. (Note for next time: it would work better to remove the outer layers of clothing at this point, as most of the chunks of mud are concealed therein.) Meanwhile, empty the bathroom of anything and everything not bolted down.
3. Run a shallow tub of water. Get out towels, soap, and a large supply of washcloths. Put everything in that magical place where *you* can reach it, but the babies can't.
4. Bring the babies into the bathroom. If you forgot to undress them earlier, undress them down to diapers now. Remove diaper A and put baby A in tub. Remove diaper B and put baby B in tub. Give thanks if no diapers contain surprises.
5. If you forgot to remove the babies' clothes in the kitchen, you'll have to sweep the bathroom floor now. Don't take your eyes off the babies while you do this.
6. Grab the nearest washcloth and nearest baby and commence to scrubbing. When that one has had enough, do the other. Continue alternating until you're fairly certain you've scrubbed everything in sight.
7. Let the water out of the tub. Leave Baby B in there, stranded but triumphant in finally getting sole possession of the toys.
8. Take Baby A out and apply diaper. Discover the spots that weren't in sight and didn't get scrubbed and scrub those.
9. Take Baby B out and apply diaper.
10. Take both babies into bedroom and dress for the afternoon; read story and put them down for naps.
11. Start a load of laundry. You undoubtedly need to at this point. Replace bathroom furnishings.
12. Take a shower while cleaning out the mud from the bottom of the tub.
13. Take a nap.
It's all about learning how to maximize results from minimal efforts.