I want to buffer a signal with a 7404 IC, but this is an inverting IC. With feedback from the input to the output the signal becomes non-inverting again. Is this method correct and can it be used in circuits?
All you're doing there is shorting the input to the output which at best just passes the input through unbuffered, but might also have other unwanted affects.
You can either put two 7404 inverters in series or you can use a non-inverting buffer such as the 7407, although that one is open-collector output so you would need a pullup resistor on the output. You can see a list of some TTL logic ICs here although some may be obsolete. You can also search on one of the electronics suppliers' sites for non-inverting buffers. There are different varieties such as Schmitt trigger, open collector, tri-state outputs, and a number of different logic families for different voltages and speeds. You can learn a lot by looking though some data sheets.