Here is a 2nd method to find LCM. That I used in kumon. List the multiples of both numbers until you see a common one.
For example: 150 and 10
So the LCM is 150
Here is a 2nd method to find the GCF:
List all the factors until the both numbers have the same factor.
For example 104 and 320
Factors of 104 Factors of 320
The GCF of 104 and 320 is 8.
Personally I prefer the prime factorization method then these two,because it will take a long time to do these two methods with big numbers.