ahh cool.
I thought the attrabute spells worked diffrently. I thought it was Forces = the max number you want to augment the stats by. So force 4 to improve it by 4, with 4 being the max hits you can accept for it. The -2 makes buff spells very hard to use without focuses or spirts forced to do it for you. And you can't get a focus high enough to help with your better stats
What you say is true of all spells: the maximum number of hits you can roll is limited by the Force of the spell (unless you spend Edge on the Spellcasting roll). The Attribute spells have the added restriction I mentioned before of the Force must be as high as the Attribute is already.
Examples: if your Willpower was 3 then you must cast the spell at Force 3 or higher. If you cast the spell at Force 3, the highest you could get your Will is 6. If Will was 4 and you cast a Force 4 spell, the highest you could get is 8. If your Will was 5 and you cast a Force 5 spell, the highest you could get is 9, instead of 10 (assuming you're not a dwarf). You can cast the spell at a higher Force (say Force 5 when your Will is 4) but you are still limited by the Augmented Max.
But yes, overall the -2 makes it very hard to buff yourself. Those spells are good for buffing team-mates, though, as long as the Force you cast it at is as high as their base attribute (so buffing Strength or Body on a Troll is useless). You said you wanted to improve your Drain resist. It shouldn't be too terribly hard to get a Sustaining Focus for that: a Force 5 in character generation is only 20 BP (5 for Restricted Gear quality, 10 to purchase it, 5 to bond it). That should max you out at 9, assuming that you start out at 4 or 5.
EDIT: Or to save BP, just getting a Force 3 sustaining Focus would be cheaper (6 to purchase it, 3 to bond it, no Restricted Gear quality). If you start at Willpower 5 you can increase that to 8 with the sustaining focus. You'll probably want a second Force 3 sustaining focus to use for Improved Reflexes.
Another way to buff yourself would be to take a Possession tradition (Street Magic). This means that instead of summoning spirits who can manifest in the physical, you summon spirits to possess existing bodies. You have the spirit possess you and its stats are added to yours for the duration.