You dont need to use a schedule to water and that pot and go a few weeks to dry out.

Stop overwatering it.

I have killed SEVERAL hoyas by overwatering.

and when you water be sure that the middle of the pot is saturated, otherwise if it is dry and water is running down the sides of the pot the rootball might actually be rockhard and that could also be why you are having problems.

Ok, first of all, REPOT IT. Get rid of the soil it is in. Hoya prefer a well-draining medium. Fine orchid bark mixed with perlite and coarse sand (all found in the same area at Lowes) will do. Mix equal parts (1-1-1) of each. Soak overnight. Before potting the hoya in the new mix, soak the plant for about 15 minutes to loosen the soil (soil is not good for epiphytes, which use their aerial roots to attach to, and grow up, trees. Remove as much of the soil as you can (the more, the better). Repot in the well-draining medium.
In about a week, check the pot. If the first 2 inches are dry, water. Use a water soluble or liquid fertilizer at 1/4 strength (winter) every time you water. In the summer, boost the amount to 1/2 strength. Usual strength is one teaspoon for most fertilizers, so in the winter, it would be 1/4 teaspoon, and in the summer, 1/2.
Hope I have helped!