I use the stuff that came with the collar... I just buy a couple extra refill canisters. It's Premier Citronella Refill, found in pet stores and online pet supply under training collars.

The refill canisters are about 6 inches tall and easy to hold (think small bottle of hair spray/product). The only thing is, since it is made to refill the collar dispenser it doesn't have one of those little squirty buttons on top... you know the thing on top of the spray starch that falls off all the time ). So, I went through all the spray cannisters in the house (perfume, spray starch, etc) until I found one that fit... presto-chango a handheld doggie deterrant! There may be other sources for this stuff that come already equipped for 'combat', but this is works for me.

One of the good things about citronella, is that if blowback does occur, and it hits you, the worst thing that will happen is the mosquitos and flies will leave you alone . That is assumng that you have no allergy to citronella.

**Please use all tools in accordance with ones own health needs.