Oh yes, the Aneros is a must have! Lots of lube... lots of gloves... condoms for toys... I highly suggest just going slow with the guy... don't do this with long nails... I always keep mine short...
My fave lube so far is the KY warming jelly. It varies from guy to guy, but if he isn't sure which position he likes to receive prostate massage in, just try different ones. I've found most guys like to be lying on their backs to take pressure off their backs.
I highly suggest using your finger first so you can learn where the prostate is and how it should feel before using toys.. then you have an idea on how far in you need to go.
Also, you can feel when a man is about to cum because his prostate will swell even more and push your finger down or the toy down...
Just some helpful suggestions... if you wanna pick my brain even further, feel free to PM me. Have fun.. it's really a fun twist on things... oh and wait til you wanna try strap-on!