If you do not have the time to do this for 2 hours, do it as along as you can. Any amount of time is better than none at all. If you do not have a bucket, any large container will do. If you run out of room for water, you can take out the same amount as you put in at that point. If you do not wish to do the above, make sure that you float the bag the fish come in, in your tank for at least 20 minutes so they get adjusted to the difference in temperature.
Temperature is probably the most critical of the factors.
Once the fish is placed in the new tank, observe the other fish. Pay close attention to see if the other fish chase the new fish around. Some amount of chasing around is normal. The fish need to get their pecking order in place once again. However, if the new fish is being attacked as well as chased continually, the chance of the new fish surviving this aggression are very slight.