I posted this elsewhere in another thread the other day, but I will post here too. I got a 1 1/4" vacuum hose from the pool store. On the end that swivels and attaches to the vacuum head I wrapped a few rounds of electrical tape around it in order to make for a snug fit in the Intex vacuum head (the one that came with the pool). I pushed that into the vacuum head where you normally tie on the mesh bag. The other end of the vacuum hose will fit into the hose that goes to the skimmer basket that hangs on the wall. I don't know if it will fit directly on the intake but you could try it. I put the hose in the pool, and then hold it over the return for a minute or two with the filter on in order to flush out any air, and then connect it under water. I also take a knee high panty hose and put a few inches into the hose before connecting it to the skimmer hose to make a "bag" of sorts to catch the debris. Otherwise it will all get caught on the screen of the intake and it's hard to clean off without it all falling back into the pool.
This method worked well for me with the smaller Intex pump that came with the pool. I've since upgraded to the sand filter and it works much better now with more suction. I just had to cut the grate off of the intake so that the leaf basket on the filter could catch the debris instead of clogging up the intake, so now I don't have to use the pantyhose and empty it constantly while vacuuming if there is a lot of dirt (which there usually always is...the fun of living in the woods!)