I learned a nifty trick the other day. If you need to run a pull string through a length of electrical conduit, there’s a faster, easier way than pushing the string through with a fish tape (the way I’d been doing it for a very long time). Use a shop vac to blow the string through. One advantage of this technique is that you can quickly get the string through very long sections of conduit.
You’ll need duct tape, a couple of baggies and some pull string (you can get the fancy pull string if you like but any lightweight poly cord also works fine).
Cut a hole in big enough for the shop vac hose in the closed end of the baggie and tape it around the hose.
Cut another hole just slightly larger than your pull string and insert one end of the string in the baggie and pull it out the open end.
Now make a “kite” to help the air carry the pull string though and attach it to the string. For small diamater conduit those disposable foam air plugs work great. For larger conduit, you can use a pingpong ball if you have one handy or a little parachute made from another baggie.
Insert your “kite” into the conduit and tape the end of the baggie around it. Insert the shop vac hose into the blower fitting and turn the vac on. The baggie should form a relatively airtight seal around the conduit and the string will carry through the conduit as you feed it into the baggie. If the string doesn’t travel all the way through the conduit, pull it out and adjust the size/material of your kite.
When you’re ready to pull cable through the conduit, don’t forget to pull another length of pull string at the same time so you’re ready for future pulls!