I've had a new modular home for almost 2 years now. My problem? It came with custom made venetian blinds on all the windows. We're talking a LOT of blinds. I "dust" them with the vacuum cleaner soft brush periodically, but they need a deep cleaning, along with the windows after this long Winter.
Here's how to clean them easy: Pick a warm day with no wind or breeze. You need a good wide spot to lay them down (outside). I have a huge deck and lay them on that with a large sheet or plastic under them. A large tarp works great. I guess you could use the backyard lawn, but you don't want any "give" in the blinds underneath or they could get permanently bent. Make sure blinds are in the "closed" position.
Get a bucket with a couple drops of concentrated dish soap, filled with very (almost hot) warm water, and a capful of bleach. Lay blinds down on the wrong side first. Take a SOFT headed mop and "mop" each side with the soapy water.....BE GENTLE, the soapy solution will do the work. Turn over and do the other side. Rinse both sides with a hose that has a gentle spray attachment. Hang over banister of deck, or lay out on lawn to dry on a warm day.
It's fast, easy, and you can do a whole house full of blinds in a couple hours, if you have enough space to lay them all out to dry. I've done them in the bathtub before, and some of my blinds are longer than the tub. It's also very messy to do them that way. If you do them outside, all the water/mess stays outside. Window screens can be done this same way.