Do you have a metal or greyhound-style comb? They're inexpensive and might be worth investing in, because they make it so much easier to part the fur down to the skin. If her fur is very dense or she has a lot of dead undercoat built up, you might need to comb out that shoulderblade area a bit first, but you should be able to part the hair down to the skin and get the applicator tube really down in there. If you need to use a hand to hold the hair apart, you can wear gloves if you're concerned about getting it on your own skin, but these products are considered non-toxic to humans so that's up to your own comfort zone (definitely wash afterwards though to avoid getting it in your eyes or mouth or somewhere else more sensitive).