Most major fish selling stores will have the thin pipe used in UGF to hang the air-stone from the top. That little capillary tube. Simply take a length of it long enough to penetrate from above the water to the bottom glass and cut the tip off at a sharp rake. You can then put a small air pump on the back end if you're using rough sand or fine fluorite.
If you're using actual dirt I suggest getting a small hand pump like walmart sells for siphoning gas and pumping open aerated tank water gently under the dirt. Pressuring it under the dirt. This produces roughly the same effect as the plants cycling water through the bottom. Be sure to run tons of water through the hand pump first to get it clean. You're looking at doing this in a 15mm grid in every portion of the dirt that is not actively planted.
Alternatively you can do "thin layer" natural planting. I used this on my community tank. I applied just about one inch of hand sorted potting/top soil in the bottom of the tank, pre-mixed by hand with clean used aquarium water. I then scooped out a large bag of fine black fluorite on top, this also pre-wetted, giving me about an inch and a half of substrate but with the top half "self aerating". So I have the benefit of actual soil but with a low risk of cyanosis and other decay bubbles. I still had to penetrate the soil mixture from time to time as it seems the "dirt" I got was actually compost. You want NO compost - especially not mechanical compost where they've ground up the compost then let it sit - it rots.
I've got almost 2 inches of total soil combination in that planted tank now, the plants are very healthy and from time to time I'll dig in with a bent fork to lift up the ornamental gravel.
The thin layer seems to also encourage my crypts and red wendtii to spread wide and send up shoots a lot faster than normal. The tank has produced several new crypt and wendtii which I was able to transplant. The spot where I removed one large one was occupied by another within a month.
The compost caused me to suffer several oscillations in alkalinity and the original planting over a year ago made it to last month before the plants used up all their "dirt".
Which brings up what I did to replace the "dirt"... Cake decorator's kit! I squirted another ten cups of mud down into the bottom layer.
From what I've read, using the pipette method works well and lets you get through root systems to pockets under plants, but I've also heard of using an actual stainless steel long-handle tea stirring spoon. The kind with the dime sized head and ten inches of handle. You can feel any roots that it bumps into instead of willy-nilly poking but it requires much more time.
Best option: Plant it all, carefully, then remove some plants and let others die from competition.