Lots of discussion on drafting (how to gain the draft, stay in it etc) on thing that worked a bit better for me is to choose the view where you are looking back at yourself.(keyboard #8 i think) , if you let the person/bot pass and you can still maintain them on the screen in front of you it seems to hold the draft. You will see your rider "sit up " a bit and at times take a drink of water, hence letting you know you are in the draft.
Trying to draft is a bit like being at the end of a pretty long pace line. Surgy Group dynamics are impossible to feel, and its purely a virtual guess on space. I have yet to find a true pack of riders, which I suspect would be a bit easier to maintain the draft