It is easy... Use the tried and true internet method...

Boil a pot of water. Once it is boiling - place the Hogue grip in the boiling water. Use a spoon or something to hold it under the surface.

Leave it in for 60 seconds. Then, remove it and briefly dry it.

Then, install. It's not hard at all. It stretches more when how. Then, when it cools, it tightens up a bit.

I use the Hogue Jr on double stack guns. Hardest one to get it on was the P99, as the magwell is a little wider at the end. My Hk P2000 has one. My PX4 has one.

Those are doublestacks, and they ARE hard to get the grip on. The Shield - that was easy. Even the Shield Plus only took me a few minutes to get the grip on.