I've worked quite a bit with RS485 with various protocols for the security camera business.
As far as the cabling is concerned CAT5 or CAT6 is a pre/requisite if you want more that 50 metres. Less you can get away with twisted just about anything. Also, from experience I have found that over 100m you should not have an earth connected on each side (only 1 side) as you can get earth differential and as RS485 & RS422 only allow around 1.4 volt differential the difference in earth can cause false data very easily.
As far as multi slaves is concerned you can have up to 31 slaves all talking on the same time but you may will have to have to make the master poll each one's address and allow him to answer in turn or just let each one repeat his message over and over until the master hears it without a clash (camacazi way but can work with out 4 -5 nodes).
I found the best cable to use (noise resistant and reliable) is the CAT5 shielded type where each twisted pair is separately shielded. I've never had problems with that and I have send data, sound, video & power over the same line without problems.
I usually use the very inexpensive 75176 from Texas Inst., an old but reliable chip which is very much cheaper than the MAX. For dual direction you just use 2, one for each direction.
One thing that cannot be done without a real intelligent RS485 repeater with it's own handshaking system is BI/directional communication with multiple masters and slaves mixed together. (In theory RS485 can have up to 31 masters & 1 slave or 31 slaves and 1 master for a wire length up to 300m, any more and you need a repeater) this is very different to RS422 which is a single master with slaves system. Many people lump them together even though their logic voltages are also slightly different.

I hope that little 485 lecture helped a bit.

Best Regards

Chris