I have listed out several tools I use and I’ve marked for what I use them with as C-conifer and D-deciduous. With the exception of the belt sander most households will have them all already. If you don’t have one be creative a little lateral thought goes a long way.
(D-C) - Sharp whittling or hobby knife (extra blades)
(D) - Wire Cutters
(D-C) - Tin Snips or a good “Cut Anything” type pair of scissors
(D-C) - Small pair of good hobby type scissors (Fiskars or similar)
(D) - Mini Spatula (coffee stirrers work great too)
(D-C) - Paint brushes, the small hobby type.
(C) - A cheap wood rasp or file (If you don't have the belt sander) (I use a small 7 inch one; curved on one side flat on the other, it has both fine and coarse teeth and was about $10) It is also excellent for terrain work.
(C) - Sandpaper (med and coarse grit if you don't have access to a belt sander. You may want a piece anyway, handy stuff.)
(C) - Electric drill (or rechargeable) (optional too but helps out even more than the belt sander)
(C) - Wire Brush attachment for the drill (A good steel one not the brass or light wire mini Dremel type. Dowels are hardwood.)
(C) - A metal Curly Kate or Scrub Bud pot scourer if you don't have access to a drill. You can also use the coarse teeth of the wood rasp.
(D-C) - A good quality Spray Adhesive This is one of the more important ingredients as you want good bonding strength but flexibility. I like Elmer's brand it is low cost, readily obtainable, and works on my styrofoam terrain too. Watered down Weld-bond works too, but it is harder to work with and you really need to devise a mist type sprayer for it.
(D) Thick latex or acrylic based flexible filler. Probably the best I've found so far is Flex-Paste by Woodland Scenics, kind of expensive though. I have had great success using Fimo and/or Sculpey type material too but these are not flexible at all, (apparently one of these companies has a flexible line, but I haven't tried it yet). I have also used paintable acrylic sealer from the hardware store too, (plus this stuff only costs a buck or two).
(D-C) - Spray Paint - Three types, plus, needed - Primer (I like ruddy brown or red oxide colour), A Flat Matte Black, and a clear Matte Lacquer. Also any nice flat or matte browns you can find; avoid gloss and satin paints, as they are just too shiny and you won’t be happy with the results. Additionally, or if you can’t find other usable spray paint browns, you may want to use your acrylic paints with a brush or your airbrush if you have one to do some finishing detailing prior to applying the lacquer coating.
(C) - Sisal - Sold everywhere as garden twine and as rope. Note, do not confuse it with jute. There are many thicknesses to choose from. Pick a size compatible with what you are cutting it with. Almost everywhere carries it and old used lengths can quite often be found for free (make sure it is not oil soaked though). I have found that so far alternating between a pair of Stanley snips and some old tin snips as my hand gives out works the best for me. I've experimented quite a bit with various ideas and machines; so far cutting it by hand during a favorite TV show works the best.
(C) Washable, cut to size, Permanent furnace filter material. This stuff makes the best conifers. It is sold at hardware stores and places like Walmart, (buy it from the little guy even if it does cost an extra 50 cents). Most often it is a blue colour but I have seen it in brown. Large wax stripper pads work too but are more expensive and a bit harder to work with.
(C) Some “fine” fiber filter material or a worn out pot scourer pad.
(C) - Wooden Doweling - I use 1/8”,1/4” and 3/8” the most. As much as I hate to say it Walmart was the cheapest for these, they were also the longest pieces. Michael's was the most expensive and the shortest length, shop around. Save your old round paint brush handles.
(C) - Round tooth picks - Used for the 1” - 2” conifers. They come already pointed and there is really no need to do any extra work to them. In general, they are extremely handy in the modeling-painting world, so you should already have some.
(D) - Old lengths of extension or appliance electrical cords. (Check behind the junk store or walk up the street on garbage day with your wire cutters.)
(D-C) - And of course flocking; coloured leaf material. I use Woodland Scenics stuff quite a bit. It is readily available at most hobby stores. I use the fine turf and the foliage types. I have tried the clumping material with a fair amount of success too. There are some other materials out there but I have yet to see them at a store anywhere near me, usually you find them in small ads in some model railroad magazine. I’ve had good success using stale spices and herbs ground to the right size. I have not been able to figure out how to grind up foam rubber small enough yet or how to colour it. Fine sawdust also works and it you can dye.
(D-C) Old newspapers for mess control.