Never prune before blooming except for dead wood unless the plant is really struggling. This will remove all of the spring flowers.

The best time is right after blooming, like now. By mid summer they will be starting to set next years flower buds.

Here is a link that might be useful: How to grow rhododendrons and azaleas.

Thank you Rhodyman - I will continue to research on this.

It makes sense to prune after blooming. However - there has already been much growth of new leaves just after blooming. It's okay to prune these off now? I'm assuming that new growth will not begin to fill in until next spring, correct? In other words, all the new growth this year has already occurred? - (except for flower buds, as you suggest...?) I'm looking to reshape slightly and avoid legginess.

Thanks!

The buds normally form in mid-summer. You may loose some bloom, but you should get new buds forming on the remaining parts of the plants. You obviously are loosing the sites of many buds, but other sites will develop new flower buds.

For legginess I am assuming you mainly want to cut the top. The rest will fill in. The top won't have as many flowers but the sides will have more. It is a trade-off.

Grasswhisperer, as Rhodyman pointed out, flower buds are set in mid summer.

Pruning will cause dormant buds at leaf axils (where leaf joins stem, or where there once were leaves joining stem if cutting below any existing leaves) to swell and emerge.

Dormant growth buds should begin to grow within a month on smaller limbs, as many as 10 weeks on large main trunks. So you will have new growth following your pruning, those buds are not going to wait until Spring while leaving you with bare stubs the remainder of this year :)