Looks like you and have something in common. I am like a walking manual of trauma treatment and care. My medical file looks like the Enclopedia Britanica. It is just about as many volumes.
For working on your lefty shooting I wold say load your 642 with some real soft shooting .38 spcl full wad cutters. Then get a pocket holster for it. While not being uber fast with it you have it. Besides when walking with your hand in your pocket it looks like you are well walking with your hand in your pocket.
Also a pocket holster is cheap, and can be used in the pocket of either side.