Unless you compress your images for minimum file size, if you frequently inline all your images, you will be deeply unpopular with users on limited bandwidth (e.g. mobile data plans). There's even one user here who posts from the ship they work on, so is using satellite data for their internet access, and a few Megs of JPEGs will cost them significant money.
With that out of the way, its quite easy to inline images - simply mark the locations where you want the images with placeholders while composing the post, attach all the image files, post it, then go back and edit it in a *new* tab so you can copy the URLs of the image attachments from the previous tab, paste them in replacing the placeholders, then select each one in turn and click the 'Insert Image' tool.