hmm…well i think i went into detail two different times but i’ll explain myself as much as possible to get this question out of the way for future references.
to perform AG (advance guard), you must press 3-6 buttons during a 12 frame blockstun (single hit). 12 frames is the minimal any move hits in the game. when a move says +3, that is the advantage given to _____ character AFTER all the frames it took for it to come out, hit, and retract. so do not get confused by this.
depending on when it decides to actually perform the AG is random. there is a percentage you can do to increase it, and if you do the hardest you can ensure that it will come out. but i only know one person in japan that can actually use 6, so it is extremely hard. not to mention, on GGPO it makes it even harder (trust me, it makes a HUGE difference). the average player on GGPO only goes to 4. at the arcade, japanese players go up to 5.
now with some of that explained, here are the ratio percentages.
3 = 25%
4 = 50%
5 = 75%
6 = 100%
now, the strength of the button it decides to land on (IT DOES NOT HAVE TO BE THE LAST BUTTON YOU PRESS, IT CAN BE IN THE MIDDLE OF YOUR SEQUENCE) is how far the opponent will get pushed back. weak punch and kick only push the opponent about 1 and 1/2 character spaces in front of you. strong is around mid screen with your corner backed to the wall, and the strong versions push them around 3/4 of the screen.
the most typical way of performing AG’s and preferred by most stick players is this. LK LP MP HP (HK). the HK is in parenthesis because it is not typical to go to 5 buttons online, but it is optional if you are at that level. i know this will definitely feel weird drumming the reverse way, coming from 3s i usually drum right to left. but, this is fact very very useful. if you are downblocking, you will get a short if they did nothing. you can also tech throws with this method of AG. and if they try and jump, the average short will recover enough until you can block again. personally, i do this by thumb on lk, index on lp, middle on mp, and ring on HP and slide to HK.
another method is scraping across left to right, then right to left once. this is best done with a glove, and if not you can use your knuckle closest to your fingertips. pretty self explanatory. 3 hits across, 3 hits back. you have to be good and this way is pretty energy-consuming.
another is LK MP HP HK. the problem with this is that it only goes to 4. but 4 isn’t a bad number at all, it is very good if you can get 4. so with that said if this way works best for you, by all means use it. flick your wrist in a clockwise motion for the best effect. from LK MP HP then slide from HP to HK. personally, i do index on LK, middle on MP, ring for HP and slide to HK.
the last method that i know of is using MP MK HP HK. first, straighten your index and middle finger out. the middle knuckle of both fingers will be pressing MK and HK. the tip of your fingers will be pressing MP and HP. start with your index, slide with your knuckle to MK. then do the same with your middle finger. if you want more inputs for tech block, you can use your index finger to go back up from MK to MP again for a full 6 inputs. the only drawback to using this method is that if you whiff, you will whiff a MP. that can be good or not good depending on your character.
hopefully this clears things up