Powder was a dream when it was plentiful, kinda iffy to deal with that stuff right now. For the guys that are even around, and who will actually give you more than 10g without bending you over, the market isn't what it was 5+ years ago.
Walnut oil was my favorite, but grapeseed and the like works fine, I even used veg oil once in a pinch
I think syringe filters suck, they just suck. Get a big 250-1000mL setup, a brake bleeder vacuum with a gauge on it and its cooking time

Don't apply too much vacuum or you'll bust your plastic goodies, the large the container the more a problem this seems to be. If its warm, i.e. ~100ºF it will filter quickly. Don't go putting 130º+ super hot stuff in there, ahem.
No, powder is not more plentiful but it does still exist. After all, there is a LOT, ok a SHITLOAD of profit margin in a prepared product. A mere 100g powder will give you 20 bottles of 250mg/mL goodies.