" first, it’s hard on my knees and back to stoop down to spread granular
as a side dressing, then get down there to cultivate it in"

Why would you do it that way to begin with? Got a hoe and/or rake? Make a shallow trench in the soil about 3-4" out from the plants, lay the fertilizer in the shallow trench and lightly rake the loose soil over it, water well. Depending on how well your garden is laid out and the plants with similar needs are grouped you can do a 50' row in about 10 mins - and without ever getting down on your knees. ;-)

As for the fert used - you don't compare granular weights to liquids. They are totally different animals. You follow the directions on the specific liquid you used.

But using a hose end sprayer sure isn't the best way to apply liquid ferts. That is foliar feeding and while foliar feeding has a role in gardening at times that role has specific applications, not routine feeding. You can burn leaves AND much of it is wasted as it never gets where it needs to go - the roots. If you don't have a drip system you can run it through then you mix it up in containers per the directions and pour it around the base of the plants or along the row.

Dave