i had hornby dublo 3 rail stuff and marklin 3 rail and stud contact - for those of you that dont know the rails are made with a tinplate with rails attached, there is a third rail in the middle .these were common before the widespread use of plastics as insulators .the third rail was a conductor and the engine had a pick up on the underside to complete the circuit , later developments meant the axle of the wheelsets could be insulated so both rails could be used at once with out the need for a third rail. in 1952 marklin changed their 3 rail system to stud contact where the third rail ran under the track and a stud popped up through the tinplate ballast every 5mm much more realistic than the third rail(marklin is also unusual because its locos operate on 21v ac rather than the normal 12v dc) fortunatly like fish keeping there has been some amazing advances in technology.
livingart i had a 4'x8' layout when i was 10 sadly as i grew older it fell into disrepair and was sold. again like the fishkeeping i think the major attraction i had to it was the technical side, the diy and modifications rather than the trains themselves. i have a box of old model railway magazines that i have to put on trademe at some stage. unfortunatly i cant help much with ballast and the like as so much has changed since i was in the hobby that there is probably a way 10 times easier than the methods i know of