Best method / time for top working guava

[gnappi]

So far I've had no fewer than 6 "Mexican cream" guava that none have remotely resembled the MC. My latest is a green skinned VERY pink meat very lacking of any hint of sweetness. Gads, talk about mislabeling fruit? I'm done with trying to find a MC.

Anyway, I have a very healthy Barbie Pink that has yet to fruit as well as a "Thai white"  and "Ruby supreme" and both are in a bad location to get the care the Barbie pink does and they look it. 

So... I want to take cuttings from the Thai and RS and graft onto the Barbie, then pull the other two. What's the best method for top work / grafting? All of them have hardened wood in most areas, and some green stems showing. 

[spaugh]

Did you ever do this project?  I want to top work a mediocre guava tree also but not sure the best way.  I had zero success grafting guava in the past.