you could use a hammer but you will more than likely make a mess of it as it needs a fair anount of wacking{sorry to get technical}to get them in, one slip and you will say bye bye to threads. best bet to save money is to put the car safely on stands,and take the hubs of yourself{if you know how?)and get a mechanic or engeneering place to press them in.
can be done with hammer and the right size metal tubes.but i speak from experiance.i had to change a couple of broken stud's on a racecar and was away from the workshop at the track.got the old ones out,got four in and was halfway with the 5th and it slipped when i hit it and stuffed all the threads.pain had to do it all over again.