Although I got a message warning me that this topic has not been posted in for at least 120 days, since it seems to be the right one to post my questions and it has so much useful information, I will post here so your answers don't get lost for future readers (if I'm doing something wrong by posting here, please let me know so I don't make the same mistake again).
So my case is as follow: I'm getting next month several varieties of mango from Florida in order to graft them in Gomera 3 rootstocks. I'm planing to get about 3 scions of every variety to increase the chances of getting 1 success graft of each. After reading the whole 34 pages of this topic and some others in the forum, and watching several videos in youtube I think I'll try cleft grafting in most of the cases, but I'm thinking of trying as well some veneer graft. (I've being practincing with mangoes branches and graft seems easier to me).
My doubt is if is a good idea to make at the same time 2 veneer grafts in the same rootstock. I'm afraid that this could actually reduce the chances of having success since rootstock have to feed two scions instead of a single one, but I do not have experience grafting mangoes, so I might be wrong. I know people that make 3 chip budding grafts in the same peach rootstock, in order to ensure that at least one succeeds. I'm wondering about that because I have to drive quite a long distance to get my rootstocks and there is a limit of space in my car. If I could graft two scions in one rootstock, I would save space and money.
Second doubt is about fertilisation, I read some advice in this topic about using fertilisation to push the scions growing. My goal here is only to maximize the chances of the grafts succeeding, so I would like to know if fertilisation actually increase or reduces the chances of success. If it do increase it I'm wondering if using guano is a good idea. I used recently for very small seedlings of papaya that were getting yellow, and they seem very happy with it, growing now green and strong.