Hardboard is easy and cheap but doesn't last as long. I've made several out of 5/8 ply. Some like acrylic.. but whatever you use, get a good master and dupe it. Never work off your master. I've made thatmistake and blew out a 50 dollar template I purchased. Luckily I had made a decent copy so I just made a new master, but still - it was a headache.
On tearout and router bits. I had almost written off routing because I had ruined 2 ash bodies but having a good bit makes a huge difference. I bought a brand new 2" 1/2" shank flush trim and I have never had tearout. Minor tearout in figured wood, so that's still an issue, but in regular body wood you should be ok. Ash is prone to tearout because of it's grain structure so you have to keep the wood in mind too. If you really want to be careful, pick up a spiral flush trim. not cheap, probably 40-50 pounds in uk. they are about 80-100 bucks here in the states. The up or downward cut motion though will slice the wood rather than pulling it away from the edge.
Last thing on patterns, making your first out of MDF is nice as it cuts easily and sands really smooth, then dupe it onto ply or something for a durable master. You don't want to work off the MDF ones as it will burn and if it ever gets wet you're screwed.