By spray,, you're being a bit vague. Are you talking blown in cellulose insulation? Or are you talking about expanding foam insulation?
Blown in insulation is rather easy, but putting it into wall catities in some areas and some kinds of construction can be detrimental.
Cellulose insulation will hold condensation in humid areas quite badly and can cause wood that it's in contact with to rot..
Expanding foam can if over-used expand so much it actually buckles walls..
So my advice is to read about and look at what you are doing before you head in.
If you are talking about blown in cellulose, the suppliers sometimes provide the equipment free of charge for a given time frame..