Hollytone is an excellent fertilizer for all acid soil plants which I have used for more than 25 years. Now is not a good time to fertilize; it's not necessary and can stimulate new growth which will not harden off in time for winter. I fertilize in early spring, but some advocate doing it in late fall when plants are dormant. It can go right on top of the mulch - follow the manufacturer's recommendation for the amount per plant.
The most important thing you can do is to keep the plants well watered right up until the ground freezes. While millions of cubic feet of peat moss are sold each year as a soil amendment, it really isn't great for this purpose. It tends to be too fine, breaks down quickly and, worst of all, is very difficult to rewet if it dries out.Aged/compostedbark is a much better soil amendment and is, I think, also the best mulch.
Protecting these small plants from winter sun and wind with burlap screens, evergreen boughs, etc. for the first winter or two is a good idea.

Use three to four inches of the mulching material you have already purchased. Do not pile it right up against the trunks of your plants.

Water deeply and thoroughly, remember the water has to get through the mulch, too. Don't water frequently enough so that the soil stays soggy.

In my many years as a grower (but not an expert), I have concluded that azaleas do quite well without added fertilizer. My care consists primarily of keeping lots of organic mulch and water on them. I agree with maingrower, when it comes to late fall (and even winter) watering. If the ground isn't frozen, make sure it remains moist. Azaleas are more susceptible to drying winter winds than are most plants.

It always amazes me to see azaleas planted in the middle of lawns in full sun. Lawns need sun and alkaline soil. Azaleas thrive in shade in acid soil.